ESSOINS ON THE EYEl 
 
 .i.;^^. 
 
 M. B. KETCHUM, M. D. 
 
UNIV 
 
 OF THE 
 
 OF 
 
 iXTY 
 
 ^FOR^ii 
 

 aZ-^Ul/ ^^^-^i^''-^' 
 
 
Ketchum's Lessons 
 ON THE Eye 
 
 Dedicated to the "World of Optometry" and 
 
 Especially to Those Who Have Sacrificed 
 
 Their Time and Energy to the End 
 
 That the Word "'Qptometrist" 
 
 May Be Honored by All 
 
 Other Professions 
 
 the contents of this book has been 
 especially arranged to meet tfie 
 present day needs of the optometry 
 student, it covers the essentials 
 OF the "structure and function of 
 the eye, the orbit and its appen- 
 dages". ALSO the diseases OF THE 
 
 eye that he should recognize 
 
 Edited and Published by 
 
 MARSHALL B. KETCHUM, M. D. 
 
 President and Founder of the 
 Los Ans^-eles Medical Scliool of Oplitlialmolog>' and Optometry. 
 
 Los Angeles. California. 
 19 2 
 
JicluiOli 
 
 fiDtf.raetrists 
 
 a 
 
 RE 51 
 K4 
 
 UBRARY 
 
 A FEW APHORISMS 
 
 ()1'T()Mi^:trv, today, is the highest conception 
 
 THAT those best OUALIEIED TO KNOW, THINK 
 IT IS. 
 
 WE CANNOT HARMONIZE OUR TEACHING WITH THE 
 student's capacity for LEARNING, NOR HIS 
 IDEAS OF HIS SPECIAL REQUIREMENTS. 
 
 DO NOT BE IGNORANT OF YOUR IGNORANCE, BUT 
 KNOW THAT YOU KNOW. 
 
 THE KNOWLEDGE OF OPTOMETRY MUST COME TO 
 THE STUDENT IN AN ORDERLY WAY. 
 
 ALL THINGS ARE DONE BY THOUGHT. 
 
 THE DIFFERENCE BETWEEN THE OLD-TIME REFRACT- 
 ING OPTICIAN AND THE OLTALIFIED LTP-TO-DATE 
 OPTOMETRIST IS EXACTNESS IN DETAIL BASED 
 UPON A DEEP KNOWLEDGE OF HIS UNDERTAK- 
 ING. 
 
 M67513a 
 
ANATOMY-iiic; 
 
 ms STRUCTURE-all or any part 
 
 ()!■ 1 he l)0(ly. 
 
 PHYSIOLOGY 
 
 1 uican.FUNCTION. The nat- 
 
 physiological] lual action of any part 
 of tlic anatomy of the 
 
 
 l)0(ly cither alone or 
 
 
 in eonjiinetion witl'. 
 
 
 any other i)ait of tin' 
 
 
 body. 
 
 PATHOLOGY 
 
 / Pertains to a diseased condition 
 
 PATHOLOGICAL\ of any part of the Ixxly. 
 
 ETIOLOGY- 
 
 CAUSE of any fault. 
 
 DIAGNOSIS— 
 
 Recoo'nition of the nature of 
 
 
 diseased conditions. 
 
 PROGNOSIS— 
 
 Jndf>nient fornu>d reiiardint>' th" 
 
 
 futui'c outcome of a diseased con- 
 
 
 dition. 
 
 Ri:xci-. r.ooKs ox ("<kxi-;r.\l AxAT()M^ axu I'lnsioLocv 
 
 Cu X X I X( ; 1 1 A .\i Morris ( ikw 
 
 Also Sii-avart'.s Maxiwl of riivsioi.ocv 
 
 .^lA^• ox Disf.a.sks of thf 1-ai:. 
 
 (iori.i)'s I'oi Isi:t Mi-huaf Du tio\ arn'. 
 
 1)i:\\i-.k's I h: \i« Axi) \i:(K. 
 
Ketchum's Lessons on the Eve 
 
 INTRODUCTORY REMARKS. 
 
 An Optometrist: — means, at the present time, anyone, wlio 
 having properly qualified for the purpose, has his practice 
 limited to the diagnosis and correction of defective vision not 
 due to disease, as well as abnormal conditions of the muscles 
 of the eyes amenable to relief or treatment with lenses, prisms 
 and ocular calisthenics. Also the diagnosis of any patholog- 
 ical condition of the eye that he may refer the case to the 
 Oculist for medical or surgical treatment. 
 
 Owing to unfamiliarity with the technical terms of regu- 
 lar medical books on the subject of anatomy, physiology and 
 pathology of the eye and the limitations of his professional 
 and legal requirements on these subjects, the student and 
 practitioner of Optometry has, as a class, been unable to "get 
 the story" as he should know it. 
 
 The Author's extended expei'ience as an Oculist, Professor 
 of Ophthalomology in a Medical School for several years, as 
 well as personally training the Optometrist from the "raw 
 into the finished product" has given him a rare insight into 
 the exact needs of the non-medical refractionist along these 
 special lines. 
 
 This book is edited especially for him and is entirely differ- 
 ent from anything in print. It is not only for the student 
 who is just enterhig this special field of endeavor, but for the 
 licensed Optometrist, as well; and we might add, that the 
 medical refractionist Avill find many features of interest to 
 him. 
 
 The standpoint from which the subject matter is presented, 
 is that of a fairly complete Avorking knowledge of the eye and 
 its appendages and is of sufficient scope to practically cover 
 all that the Optometrist will be required to know of this 
 branch for years to come. 
 
 In no sense is the minute anatomy of the eye any necessary 
 part of an Optometrist's requirements. He does not cut, he 
 does not treat, as that is the legal function of the Ophthalmic 
 surgeon, but his knowledge of the eye is required to be of 
 such a nature that for the good of the patient as well as him- 
 self and his professional associates he Avill be enabled to 
 follow his calling intelligently and know his limitations. 
 
10 Kiyiciu'M's Li:ss()\s ox Jiii-: Imk 
 
 Three main tliin«>s confront all refractionists when a patient 
 comes for advice, b'iist, does he need f>lasses oidy .' Second, 
 does he need 1 ic;i1 nuMil as well as <>]ass('s, and thii'd, does he 
 need trcatiiicnt only.' 'I'liis llic ()i)t()metris1 must know and 
 tlien act accordiiitily. Miu-li iiioie mi^ht he said, Init we leave 
 that to the student as we \'cr\ sure tliat lu' will iind herein 
 niucli of interest and value to him. 
 
 1 have planned, in my endeavor to helj) the student, to make 
 this usually dry subject a decidedly interesting one to him. 
 First, by jiresenting in picture form, Avith notes, a general 
 scheme in their proper order, of the principal parts of the 
 subject that he should master. Then following Avith a talk 
 on each pai't sufficiently explicit so that a gross knowledge 
 is methodically and easily gained. The quiz following each 
 lesson covers the essentials and causes the student to care- 
 fully review that lesson and learn to foi'mulate his own 
 answers. Having completed the general outline of the Avork 
 in this manner \ have presented in Parts Two and Three undei' 
 s])ecial headings a more intimate and comph^te consideration 
 of the individual parts of the eye that was covered by the 
 lessons, as Avell as many other features. 
 
 ^lARSHALL B. KETCHUM, M. D. 
 
Ketch If m's Lkssoxs ox iiii-: Evi-: 11 
 
 LESSON ONE. 
 
 (Section One.) 
 
 Til taking up tlio study of tlic eye it is well for the Optometry 
 .student to realize that, Avhile as a class the human eye is 
 pretty much the same in all ])eople, a "reat deal of compara- 
 tive study has been necessai-y in order to arrive at a definite 
 standard of anatomical and optical measurements and the 
 principles therein involved, so as to form a basis for considera- 
 tion from all standpoints; hence, the term "SCHE^IATIC 
 EYE" has been adopted to cover Avhat may l)e considered as 
 the perfect eye. 
 
 The following figures are given to convey at once a gross 
 conception of the eyes and tlie orbits, along with the general 
 scheme of their relationship, and this Avill lead to an interest 
 in the text that follows. 
 
 THE METRIC SYSTEM. 
 
 Everyone should l)e familiar with the metric system of meas- 
 urements. 
 
 The inch, foot, and yard system is practically obsolete in 
 anything but gross work, though the average person does not 
 seem to know it. A fiftieth or a thousandth of an inch or yard 
 is practically an indefinite quantity and the scientific man has 
 no use for it. Such a system should be entirely abolished as 
 being too crude for the present day requirements. "Decimals 
 and fractions" is the only definite, certain, and easy Avay of 
 obtaining or properly explaining any weight or measure that 
 requires delicate consideration. The importance of possessing 
 a uniform system of measures that is su]).ject to infinite and 
 exact consideration has been recognized by scientists generally 
 for some time past. In Eui-ope it is pi'actically the only method 
 in use. It is called 
 
Kktciium's Lessons ox tiil: Eve 
 
 The Metric System and in calculalioii corresponds Avith the 
 Avay we fiourc dolhirs aud cents. Jt is founded on the Avord 
 metre, wliich is the unit of length, based on the measuroinen, 
 of llic iiuadrant of a meridian of the earth. There are only 
 three parts of this system that we usually use in our ordinary 
 ophllialniic and optical nieasui'cnicnts. They are — ^Feti'e. 
 Centi-nietre, INIilli-metre. Study this table a few minutes and 
 you will have it. The Optical houses furnish small ivory rules 
 and caids showing by measure exactly, centi-metres and milli- 
 metres as compared with the inch system. 
 
 IMetre Centi-metres 
 
 1 = TOO 
 
 !^^illi-metres 
 1000 
 
 Explanation — The smallest decimal we use is 1 niillini-.'tre 
 (mm.) and it takes 10 nun. to make 1 centimetre (cm.) 
 and that's all there is to it. (^onipaied with the inch system, 
 the optical student should be able to transpose from one to the 
 other. It is as follows : 1 m. = about 40 inches (1 yard and 4 
 Inches.) 25 mm. = about 1 inch. If 10 mm. = 1 cm., then 
 it would take 2:-') em. to make 2.1 mm. or 1 inch. 
 
 In all optical problems these ivlative measures are used. 
 Kclalive to the dollar system, it is like this: 1 meter = 1 dol- 
 lar; 1 centinieti'e = 1 cent; 1 mm. = 1/10 of a cent. Now 
 looking at a rule with millimcties ami centimetres. marked oflf 
 on it yon Avill become familiar by sight just what each one is 
 as to dislanee. Here it is. 
 
 Inch System 
 
 Metric System 
 
Ketchum's Lessons on the Eye 13 
 
 Figure 1. 
 
 Every normal person has two eyes, (either, being a perfect 
 mate for its fellow eye) so situated in their respective posi- 
 tions in the head as to be parallel one with the other and 
 under such control of the eye muscles as to Avork and move 
 together in perfect relationship when looking at objects at 
 any and all distances. 
 
 They are located in the upper and front part of the skull, 
 each in a bony cavity commonly called the orbit (eye socket). 
 
 The distance between the two eyes varies somcAvhat in dif- 
 ferent individuals, OAving to the fact that the general measure- 
 ments of any tAVO heads are not identical. HoAvever, in the 
 average adult, Ave usually find that from the center of one 
 pupil to the center of the pupil of the other eye, (called pupil- 
 lary distance — abbreviated P. D .) it is about 60 millimetres, 
 while the average range of distance betAveen the eyes is from 
 56 mm. (214 inches) to 60 mm. (21/2 inches). 
 
14 
 
 ^oxs ox liii'; 
 
 Figure 2 
 
 Figure 2 is to illustrate the fact that although the two eyes are 
 ];arallel the two orbits are not i)arallel, but diverge from one another; 
 also that in front (the base) they are somewhat oblong and irreguhir in 
 form and droop downward. 
 
Kktchum's Lessons ox tiik J'Lve 
 
 15 
 
 Figure 3 
 
 Figure 3 is to sliow tlie position of the orbits and how the ej-es lie 
 in each orbit and are held in a position of parallelism by the muscles 
 that control their action. See also how they are connected with one 
 another where the optic nerves join, inside of the skull, and connect 
 with the brain. 
 
16 
 
 Ketciilm's Lessoxs ox 
 
 HE E^ 
 
 A' J- r.f. 
 
 Figure 4 shows front view of the right eye in the orl)it and how the 
 muscles hold it in its proper position straight ahead, and thes:e muscles 
 are so arranged that the eye can be moved in any direction with the 
 slightest effort. 
 
Kktciium's Lessons on Tiiii Eve 
 
 17 
 
 Figure 5 
 
 Figure 5 shows the eye surrounded by a soft cushion of fat which 
 offers no resistance to its movements in any direction. It also acts as 
 a support to the eye. 
 
18 
 
 Ki:tciium's Li:ssoxs ox tiik Eve 
 
 Orbicularis oculi 
 
 Rectus 
 superior 
 
 Levator palpebr^ 
 
 bUPERIORIS 
 
 Figure 6 
 
 Figure 6 shows a view of the right eye from above — top of skull 
 removed. The position of the e.ye-ball within the orbit along with the 
 arrangement of some of the muscles that control its movements. 
 
Ketchum's Lessons on the Eve 
 
 19 
 
 Obliqut-S superior 
 
 \ Levator palpebre superioris (cut) 
 
 ^ Rectls superior 
 
 Rectus lateralis 
 
 Obliquus inferior Rectus inferior 
 
 Figure 7 
 
 Figure 7 sliows side view of eye and muscles which gives an idea 
 how the eye-ball lies within the orbit. 
 
20 Kktciilm's Lessons ox thf, Eyk 
 
 The net of S(>oiiig distinctly is a peculiar one and involves 
 many tine points for consideration. Figure 8 is a sketch 
 made to illustrate the fact that the eye alone is practically 
 only a medium through Avhich vil)rations of light coming from 
 some object outside of the eye are properly adjusted -svithin 
 it. These visual sensations are then conducted on through 
 the optic nerve, to Avhere it joins the optic nerve of the 
 fellow eye at the optic chaism (O.C.), where all points are 
 fused together, and from there on through the right and left 
 optic tracts to different lobes of the brain where the "sense 
 of sight" is located. The diagram shows hoAv the correspond- 
 ing sides of the retina are united — at the optic chaism — by 
 crossed fibres and accounts for the "field of vision" in each 
 eye and that objects seen with both eyes are united where 
 the optic nerves meet, the fibres on the right side of both 
 nerves uniting thei'c, and after union going thence into the 
 brain in the nerve Mhich is on the right side of the head, and 
 the fibres on the left side of both nerves uniting in the same 
 place, and after union going into the brain in the nerve which 
 is on the left side of the head, and these tAvo nerves meeting 
 in the brain in such a manner that their fibres make but one 
 entire species of picture, half of Avhich in the right side of 
 the sensoriuni comes from the right side of both eyes through 
 the right side of both optic nerves to the place Avhere the 
 nerves meet, and from thence on the right side of the head 
 into the brain, and the other half on the left side of the sensor- 
 iuni comes in like niannci' from the left side of both e\es. 
 
 HEREDITY. 
 
 The influence of heredity on the eye and its appendages is 
 particularly noticeable in a great many families, as recent 
 studies show more and more the tendency of the offspring in 
 many Avays to i'eseml)ie the parents even in the most minute 
 details of structure and this fact deserves careful considera- 
 tion as this subject has not been giA-en tln^ critical stutly tliat 
 it deserves. 
 
 At birth the two liuinan exfs do not woi-k in perfect har- 
 mony togetlicr. .Mi'aniiig that the inlliieiice ol' the action of 
 the muscles 1lia1 liohl each one in ])osition, is not inider any 
 kind of conlnil, j)liysiologically sj)eaking, at this time; so that 
 the infant iiia\, \-ery early in life, look more or less cross-eyed 
 nntil tlie iicecssity for binocular fixation comes into pla\. In 
 llie eoiiisr of from si.\ iiioiiUis to a veai', as the e\('sii>jit (level- 
 
Figure 
 For description see page 20. 
 
Ketchum's Lessons ox the Eve 21 
 
 opes along with the slowly growing intellect of the child it be- 
 gins to take notice of moving objects and directs its eyes to- 
 Avard them, and thus in the course of time he learns by experi- 
 ence to judge the distance and locality of an object as Avell as 
 its physical characteristics. Seeing the same object with both 
 eyes at the same time demands certain adjustments of the ])osi- 
 tion of each eye in relation to one another in order that at all 
 times and all positions and distances by perfect fusion the two 
 images become as one. This is a physiological function Avhich 
 Avhen fully developed is called the Fusion Power. As a rule 
 this fusion power is not completely developed until the end of 
 the sixth year. 
 
22 Kktciium's Lessoxs on tiii-: Eve 
 
 LESSON ONE. 
 (Section Two.) 
 THE ORBIT. 
 
 The orbit is the first to be considei'ed l)ecaiis(> it serves as a 
 protection for the eye which is imbeded Avithiu it in a l)ody of 
 fat, this fat, hoAvever, offers no resistance to the movement of 
 the eye in any direction. 
 
 It is rather cone shaped with its base forward and the apex 
 extending: backward and inward at an angle of abont 40 de- 
 grees with the median plane, straight ahead. 
 
 Tts average dimensions are : 
 
 Depth abont 45 millimeters. 
 Horizontal (at base) about 40 mm. 
 Vertical (at base) about 35 mm. 
 
 It has four sides, four angles and nine openings, each open- 
 ing is called a foi'amen; plural, foramina. 
 
 Kaeli orbit consists of seven ])oiies wliieh arc located as fol- 
 lows : 
 
 Roof (al)ove) 1. Frontal. 
 
 Floor ())elow) 2. Superior INlaxillary. 
 :j. Palate. 
 
 Nasal side 4. Ethmoid. 
 
 5. Faehrynial. 
 
 Tomi)()ral side (i. Sphenoid. 
 7. Malai-. 
 
 As llu'ce of Ihcsc hones serve 1o I'oiin a part of t>aeli oil)i1, 
 viz.: Ihi' ffonlal, elliinoid and sitheiioid. i1 ivquiivs only eleven 
 sep;ii';i1e bones to forni holli orhils. \o1 all of each bone is 
 iiMpiired 1o form the oihit, bnt onl\ vliat is called the '■orbital 
 ])oi-tion" or i)art of tlu'se l)ones. otherwise they go tt) nnd^e np 
 Die skull. 
 
1. 
 
 Supra-orbital, 
 
 2. 
 
 3. 
 
 Anterior-ethmoidal, 
 
 4. 
 
 5. 
 
 Malar, 
 
 6. 
 
 7. 
 
 Spheno-niaxillary fissure. 
 
 8. 
 
 9. 
 
 Sphenoidal fissure. 
 
 
 Ketciium's Lessons on the Eye 23 
 
 The walls of the orbit as a Avhole fonn a strontf, bony, ring, 
 at its base, called the Orbital Margin. 
 
 The four boundaries or walls make four angles, viz.: 
 
 Superior External Angle. 
 Superior Internal Angle. 
 Inferior External Angle. 
 Inferior Internal Angle. 
 
 The folloAving are the nine Foramina, viz. : 
 
 Iiifra-orbital, 
 Posterior-ethmoidal, 
 Xasal canal or groove, 
 Optic foramen. 
 
 Of these nine openings only two concern the Optometrisi 
 to any extent and those are No. 8 and No. 9, because of the 
 nerve" and blood supply that enter the orbit through them. 
 
 The Optic Foramen is a small, round opening at the back 
 part or apex of the orbit, through which the optic nerve and 
 the ophthalmic artery enter the orl)ital cavity from tbe inside 
 of the skull, while the 
 
 Sphenoidal Fissure, a much larger opening on the temporal 
 side of the orbit serves as a passageway for the nerves, arteries 
 and veins, viz.: The third, fourth and sixth cranial nerves; 
 the frontal lachrymal and nasal branches of the ophthalmic 
 or first division of the fifth nerve, branches of the sympathetic 
 nerve, the ophthalmic veins and also lachrymal meningeal 
 arteries. 
 
 The BLOOD SUPPLY of the eye comes from the ophthalmic 
 artery, (a branch of the interna! carotid). See Part Two for 
 particulars. 
 
Kktciium's Lessons ox the Eye 
 
 QUIZ ON LESSON ONE (Section One). 
 
 1. AVhat is iiicant by tlic Icnii "schematic eye"? 
 
 2. Give averag-c P. D. lueasuronient. Use metric system. 
 
 3. What holds the eyes parallel with one another? 
 
 4. Are the two orl)its parallel, divergent or convergent with 
 
 one another in front? 
 
 5. How and whei'c are the two eyes connected with one 
 
 another ? 
 
 6. What is the cnshion of fat in the ()rl)ital cavity for? 
 
 7. Are the optic tracts in the brain or in the eye? 
 
 8. Study the diagram showing the working of the field of 
 
 vision of both eyes together. 
 
 9. At what period of life is the fusion power fully developed ^ 
 
 QUIZ ON LESSON ONE (Section Two). 
 
 10. Describe shape, position, and dimensions of the orbit. 
 
 11. HoAV many degrees do the orbits diverge from the median 
 
 line ? 
 
 12. How many bones comprise each orl)it? 
 
 13. How many bones are required to foi'm both orbits? 
 
 14. Name and locate the seven bones. 
 
 15. Why is it that oidy eleven l)ones comprise l)oth orl)its? 
 
 16. Name the four orl)ital angles. 
 
 17. HoAV many foramina in llie orl)i1 .' 
 
 18. Describe Ihe ()i)lic foranu'ii and tlie s])luMU)idal tissure and 
 
 state why lliey are especially nuuitioned. 
 1<>. AVhal aitery su])])lies l)lood to the orl)ital cavity? 
 
 :\lal<e vdur aiisweis bolli oial and written. Wi'ilten answers 
 are niueii llw besi as then you ean vvi'ry to the text to see it" 
 vou are right. 
 
3uPR^-o^!l3lT/^l- notch 
 
 OreSITAL CANAL'5 
 
 
 INfR^-0«BlTAL <_{(NRL- 
 
 b:/'^ 
 
 
 FRONTAL 130N£ 
 
 -M^i '/■ 
 
CANALOF 
 SCHLEMM 
 
 CENTRAL ARTERY 
 OF RETINA 
 
 Horizontal Section of the Eyeball. Magnified about 314 X. 
 
 The student must realize that this picture shows a half section cut 
 through the center of the eyei horizontally in order to show the inside 
 parts, thus making' the lens look oblong. Viewed from the front the 
 lens has the form of a trial case double convex lens. 
 
Ketchum's Lessons on the Eve 25 
 
 TO THE STUDENT 
 
 At this point, as you are about to study tho 
 eye-l)all, muscles, eyelids, etc., he sure to look at 
 some person's eyes as you have never done l)efore. 
 See the lids as they open and close. Notice how the 
 lashes turn up or down. See the size of the eye, its 
 color, how the pupil Avill contract and dilate, how 
 the muscles move the eye in diffei'ent directions and 
 the other eye follows it. As you take up each chap- 
 ter in study, look at the eyes again and again for 
 reference. In Part Two you will find a special 
 reference to each part of the eye, going- more into 
 detail. Memorize Part One first, then go for Part 
 Tv/o good and strong. 
 
20 Ketciium"s Lessons ox the Eve 
 
 LESSON TWO. 
 
 THE EYE-BALL. 
 
 This lesson is inercly a j>eneral outline of the eye-1)all and 
 is intended to convey to the stndent snflicient l^iiowleduc to 
 serve as a working basis for that which is most essential to 
 him at this stage of his work, so that he can at once proceed 
 to take np the study of Ophthalmic Optics and have a clear 
 conception of what li(> is doing. 
 
 The eye-ball at birth is small and nearly ronnd, although it 
 varies consideral)ly in size as well as in form. Its average 
 antero-posterior diameter is 17.3 mm., which is much less 
 than when it is fully developed later in life. The period of its 
 most rapid growth is during the first years in life; this is 
 followed by a period of slower growth, although the eye-l)all 
 steadily increases in size up to the age of puberty, and when 
 fully developed measures about 24 mm. in its antero-posterior 
 diameter and about 23 mm. in its transverse diameter at its 
 equator. 
 
 It is sometimes called the globe l:)ecauso H is so n(\n'ly round, 
 and has three coats or tunics, viz. : 
 
 Name. Part of each coat. 
 
 1. External. Sclerotic and Cornc^a. 
 
 2. Middle. Choroid, ( 'iliary llody and Iris. 
 
 3. Internal. Retina. 
 
 The Sclerotic, commonly called the 'Sxliitc of the eye" is a 
 heavy fibi'ous o])a(iuc nicnibrane and eovcM's the postcrioi' tive- 
 sixths of the ball. 
 
 The Cornea is the clear transi)ar('n1 seel ion in front and eov- 
 ei's 1h(' anterior one-sixth. 
 
 The Choroid is a Ihin layer of brown ])ignicn1, nerves and 
 blood \cs.scls and lies close lo 1he schM'ot ic, lining il enlirel.v. 
 
 The Iris is seen in Ihe fronl part ol' ill." eye diit'ctly haek ot 
 the cornea. It has an ojxMiing near its eenter, (usually a little 
 to the nasal side), called the pupil. 
 
Ketch um's Lessons ox the Eve 27 
 
 The Ciliary Body is back of and eonliiiuous willi llic iris, l)ut 
 cannot be seen from the front. It is e()iu])ose(l of two ))aits-- 
 the ciliary muscle and the ciliary processes. The ciliary mus- 
 cle is called the "muscle of accommodation" because it aids in 
 adjusting the focusing power — the lens — of the eye. The en- 
 tire second tunic is also called the vascular coat, owing to its 
 many blood vessels ; another name is the uveal tract, an old- 
 time term given to it owing to a section of the ciliary body 
 having somewhat the shape of a l)unch of grapes. 
 
 The Retina is a very thin transparent membrane contain- 
 ing arteries and veins, and lines the choroid. It is the layer 
 that receives the outside images and pictures them upon the 
 brain through the optic nerve which enters the back part of 
 the eye a little to the nasal side of its posterior jDole or axis. 
 The exact point upon the retina where all images are actually 
 focused is located practically in the center of the retina and 
 is called the macula lutea or yellow spot, (usually called the 
 macula). 
 
 Directly in the center of the macula is the principal focal 
 point of the eye, called the fovea centralis or center of focus. 
 
 Within the coats of the eye Ave find — see diagram — spaces 
 filled with fluids; the crystalline lens, etc., which may be de- 
 scribed as follows, viz. : 
 
 There are three chambers in the eye : 
 
 Anterior, Posterior, Vitreous. 
 
 The anterior and posterior chambers are between the cornea 
 and the lens, being separated by the iris but still connected l)y 
 the pupil. They are called anterior and i5osterior because one 
 is in front of and the other directly back of the iris. 
 
 These tAvo chambers, being connected, aic tilled with a 
 transparent watery fluid called the aqueous humor. 
 
 The larger chamber, l)ack of the lens, is tln^ vitreous cham- 
 ber, also called the hyaloid cavity. This chamber is lilled 
 witli a heavy, thick, transparent body called the .vitreous 
 humor. It somew^hat resembles the white of an egg in its con- 
 sistency and serves as a support to the tunics or coats of the 
 eye in order to keep the ball in perfect shape. 
 
28 Ki-.TtiirM's Lessons ox tiii-: Eve 
 
 The Crystalline Lens is a double convex, transparent, spher- 
 ical body and is a little more convex behind than in front; 
 it is located directly back of the iris on a line with the pupil 
 and in contact with it. Its purpose is to aid in focusing 
 images upon the macula. It is confined in a very thin trans- 
 parent membrane, the lens capsule, and is held in position by 
 a delicate band, the suspensory ligament, Avhich (Mitiiely sui'- 
 rounds it. This ligament is an extension of the hyaloid mem- 
 brane, which is a very thin, transparent body lining the entire 
 eyeball adjoining and separating it from the contents of the 
 large chamber which is back of the lens. 
 
 All the clear, transparent parts of the eye, namely the cor- 
 nea, a(iueous humor, lens and vitreous humor are, together 
 as a whole, called the Refractive Media, and it is through these 
 transparent, refracting media that all the images are focused 
 upon the macula. 
 
 The Optic Nerve is a long bundle of tibres coming from the 
 brain through the optic foramen into the orbital cavity and 
 enters the posterior part of the eye through the sclerotic and 
 choroid; it then expands like a cup in all directions, forming 
 the inner layer of the retina. In looking into the eye through 
 the pupil we see a round, whitish spot, apparently about the 
 size of a ten cent piece; this is where the optic nerve enters 
 the hack part of the eye and is called the optic disc; it is also 
 called the "hlind spot"". The optic nerve connects the eye])all 
 with the hrain. 
 
 The Optic Axis and Visual Line. 
 
 All imaginary line. Hie central line of llie globe dii-ect 
 through the (•.■i"i1ei' of llie cornea and the lens to a point near 
 tlie inncf niai-gin of the macula is caUed tlu' optic axis. 
 
 Thei'c is a similar tefui called the \ isual axis, which is nor 
 llie optic axis, but is the lin.' of vision, visual line, and is direct 
 from the fovea to tlic cntci' of the object look.'d at. ca.lled 
 tlie point of fixation. 
 
Ketciium's Lessons on the Eve 29 
 
 QUIZ ON LESSON TWO. 
 
 1. What is the size of the eyeball at birth? 
 
 2. What is its size when fully developed? 
 
 3. Why is it sometimes called "the globe?" 
 
 4. How many tunics? Name them. 
 
 5. Name the different parts of each tunic. 
 
 6. How much of the globe does the sclerotic and cornea 
 
 each cover? 
 
 7. What color is the choroid? 
 
 8. Is the pupil in the center of the iris? 
 
 9. What constitut(^s the ciliary body? 
 
 10. What is the ciliary muscle for? 
 
 11. What and where is the vascular coat? 
 
 12. What part of the eye receives images from the outside? 
 
 13. Name and locate the exact center of focus. 
 
 14. Name and locate the chambers of the eye and their con- 
 
 tents. 
 
 15. Describe and locate the crystalline lens. 
 IG. Where do we find the hyaloid membrane? 
 
 17. What constitutes the refractive media? 
 
 18. Through what foramen does the optic nerve enter tlie 
 
 orbit? 
 
 20. HoAv can Ave see the optic disc :' 
 
 19. What connects the eyeball with the bi'ain? 
 
 21. What is the dift'erence between optic axis and visual 
 
 line ? 
 
 22. Be sure to master the metric system of measurements. 
 
30 Kktciium's Lessons ox the Eve 
 
 LESSON THREE. 
 
 THE EYE MUSCLES AND THEIR NERVE SUPPLY. 
 
 Although the oibits diverge from one another, the eyes are 
 perfectly parallel with each other and always move in perfecr 
 unison. They are enabled to do this because each eye is under 
 the perfect control of six muscles. Altogether there are seven 
 muscles in the orbit ; the seventh one raises the upper lid. 
 These six muscles are called the extrinsic (meaning outside) 
 muscles. The upper lid muscle is called the levator palpe- 
 brarum (meaning to lift the lid). 
 
 The Extrinsic Muscles. 
 
 L External Rectus 2. Internal Rectus 
 
 3. Superior Rectus 4. Inferior Rectus 
 
 5. Superior Oljlique G. Inferior Oblique 
 
 (The plural of the word rectus is recti.) 
 
 All of the seven muscles have their origin at the apex of the 
 orbit around the optic foramen excepting the inferior oblique 
 which has its origin on the nasal side of the floor at-the base of 
 the orbit in front. The four recti muscles extend forAvard 
 from the apex an equal distance apart and are attached to the 
 sclerotic from 6 to 8 mm. fi'om the margin of the cornea. The 
 superior oblique muscle which also has its origin at the ajiex 
 extends forward close to llic nasal side of 1lie oibit to the 
 internal angle at its base and 1lien ihrougli Ihe small tendin- 
 ous pulley called the trochlea; from there is extcMids obli(|uely 
 backwai'd and over the upper and middle i)art of the eye 
 where it becomes attached to the sclerotic uiidenieatli the 
 supei'ior rectus a little back of the equator. The iiii'erior 
 oblifjue from its origin und(M' the nasal side of tlu^ front of 
 the oibit, passes below the inferior rectus and turns u]) on 
 the tempoi-al side bet\\-een the sclera and 1h(^ (^xt(M'nal rectus 
 and is attached to the seleia on its temporal side hack of the 
 e(pia1oi' of 1 lie eye. 
 
Ketch um's Lessons ox the Eve 31 
 
 The Intrinsic Muscles. 
 
 The muscles inside the eyeljall are called intrinsic muscles 
 and are : 
 
 1. The ciliary muscle or muscle of accommodation 
 
 which surrounds the horder of the lens. 
 
 2. The iris muscles, circular and radiating- ; 1lie 
 
 circular muscular fibres — sphincter pupillae — 
 contract the pupil and the radiating fibres di- 
 late the pupil — dilator pupillae. 
 
 The Nerve Supply 
 
 The principal nerves of the eye that are of interest to the 
 Optometrist are the third, fourth and sixth cranial nerves. 
 The third nerve, also called the motor oculi, supplies all the 
 muscles of the orbit excepting two; the superior oblique wliich 
 is controlled by the fourth nerve and the external rectus l)y 
 the sixth nerve. Inside the eye the third nerve contracts the 
 ciliary muscle and also contracts the pupil in the iris. The 
 sympathetic nerve dilates the pupil. Practically all the con- 
 tents of the orbit, the eyeball, optic nerve and muscles are 
 enveloped in a fibrous sheath called the capsule of tenon. 
 
Z2 
 
 Ketciium's Lkssoxs ox the Eye 
 
 Inferior obhquom\ A \ \ \\l)^<'~^sM>'i /xiir'VvW^'iV-^.r. 
 
 LacrymalglanJ^ \\ \\'\\ \^^^, /.">''= ,^,jj,p«.,-jf«Wk,-r^ 
 
 1*141 
 
 wsr 
 
 This iiiclun hit cyo— shows the general arrangement of the con- 
 tents of the orbit as seen from above. Also the optic foramen and the 
 oi)tic nerve passing through it, as well as the sphenoidal fissure show- 
 ing a direct open passage l)etween the brain and orbital cavity, wliich 
 serves as a iJassage for the cranial nerves, ophthalmic nerves, and 
 small arteries. 
 
 The wide muscle at llic top is the muscle tliat lifts tlie lid -levator 
 palpebrarum. 
 
Ketchum's Lessons ox the Evi 
 
 33 
 
 a o 
 
 
34 Kktci I um's Lessons ox THE Eve 
 
 Especial attention is drawn to the superior oblique muscle where 
 it passes through the little tendinous ring called the trochlea, and from 
 there turns at an angle backwards toward the eye-ball, where it widens 
 out and becomes attached to the sclerotic a little back of the equator 
 of the globe underneath the sui)erior rectus. 
 
 It will be seen that the insertion of the inferior oblique muscle is 
 on the temporal side and somewhat farther back from that of the 
 superior oblique. These two muscles are classed as the rotary muscles 
 whose principal function is to rotate or turn the eye on its axis. Note 
 the shape of the superior rectus. Small at its origin, becomes wider, 
 then narrow, and again wider in order toi form a broad surface of at 
 least 10 mm. where it is attached to the sclera in front of the equator 
 about a quarter of an inch— 6 to 7 mm.— from the cornea. This same 
 description applies to the other three recti muscles. 
 
 QUIZ ON LESSON THREE. 
 
 1. How many nnisclcs control the action of the eyeball? 
 
 Name them. 
 
 2. What does the term "extrinsic muscles" mean? 
 
 3. Name the muscle that lifts the upper lid. 
 
 4. Give tlie orijiin and insertion of the two ol)li(iue muscles. 
 
 5. Give origin and insertion of the recti muscles. 
 
 6. AVhich side of the base of the orbit is the trochlea on? 
 
 7. Where do we find llie iiilriiisic muscles.' Name them. 
 
 8. Name tiu' nerves llial sui)ply the luolor i)o\V('r of the 
 
 extrinsic iiinscles and whicli one of lliein also sui)plies 
 tlie intrinsic muscles .' 
 
 9. Study the two ])la1('s carcfnlly. 
 
 10. See special anatomy on nniscU^s in PART TWO. 
 
Ketchum's Lessons ox the Eve 35 
 
 LESSON FOUR. (Section One.) 
 THE EYELIDS— (Palpebrae). 
 
 Tlio eyelids arc two movable curtains placed in front of the 
 eyeball to serve as a general protection from injury, dust, 
 excessive light, etc. Along the margin of each lid are hairs 
 called cilia or eyelashes. There are two or more rows of lashes 
 in each lid, being longer and more numerous in the upper lid 
 and curved somewhat upward, while those in the lower lid 
 turn in the opposite direction, downward. These lashes should 
 never be cut or trimmed as they serve to prevent small parti- 
 cles from getting in between the lids. 
 
 Each lid has the following arrangement of parts from the 
 skin inward : 
 
 (1) Skin. 
 
 (2) Areolar tissue. 
 
 (.3) Orbicularis palpebrarum muscle. 
 
 (4) Tarsal plate. 
 
 (5) Palpebral ligaments. 
 
 (6) Meibomian glands. 
 
 (7) Conjunctiva. 
 
 Palpebral fissure is the name given to the space between 
 the edges of the open lids — (fissure means an elongated open-- 
 ing). 
 
 Conjunctival sac is the name given to the space that lies 
 between the inside of the eyelids and the eyeball because of 
 the membrane of that name (conjunctiva) which lines the lids 
 and also covers the front part of the sclerotic. It is in this 
 sac that small particles are held that get "into the eye". 
 
 Outer canthus is the name given where the edges of the 
 upper and lower lids come together on the temporal side. 
 
 Inner canthus is where the lids join on the nasal side. 
 
 Canthi is plural of the word canthus. 
 
 Looking at the lids, closely, yon will find at the inner can- 
 thus a little elevation or point on either lid where there is a 
 small hole (see picture in Lesson Five). It is called the 
 
36 Ki:TciirM's Lessoxs ox thk \\\e 
 
 Puncta larchrymalis. 
 
 This opening in each lid lends to a canal through which the 
 oi'dinary supply of lachrymal fluid called tears, is drained off 
 
 into the nose. There, also, at the inner eanthns Avill l)e found 
 
 a small llesliy spot willi a \'r\v line hairs in it. Tliis is called the 
 
 Caruncle. 
 
 Close to the inner canthus and practically attached to the 
 eyeball is a small fold of loose pink tissue which is called the 
 
 Plica Semi-lunaris. 
 
 (Plica uu'ans fold; semi-luiuiris means half moon). It is 
 also called the half moon fold. This niemhrane is the vestige 
 of Avhat in the early career of man was his third eyelid. It is 
 still fouiul fully developed in birds and some of the lower 
 animals. 
 
 The different parts of the lids besides the shin may bi-ietiy 
 be described as follows: 
 
 Areolar tissue means a tissue composed of white and yel- 
 lowish til)res widely diffused throughout the body. Its func- 
 tion is to give strength and elasticity to a part as well as 
 serve as a protection from injury. In the lids it lies next to 
 the skin and acts as a sort of a cushion to protect the eyeball. 
 
 Orbiculus palpebrarum muscle is described in Section Two 
 of this Lesson. 
 
 The Tarsal plate (tarsal cai-tilage) is a thin, eartilagimnis 
 tissue, which gives form to the lids, and, when l)o1ii lids are 
 closed, forms a shield Tor the eyeball in I'loiit. Thr eartilage 
 of the upper lid is miieh largei' than th.-il of Hie lower, and 
 at its upper margin is allaehed lo the mid of ihe muselc thai 
 lifts that lid, the levator palpebrarum. 
 
 The Meibomian glands aiv small sebaceous tfallN) glands 
 imbedib'd in the subslniiee of ihe 1ars;il earlilages and are 
 |)bice(l sidi' 1»\ side \-erlieally in each lid t'nmi one ciinllnis lo 
 the other. t'Ik'n- number aboul thirl\- in Ihe upper lid and a 
 few less, siiy idimit 1 w cnly-lixt', in ihe lowei'. These <_d;iiuls 
 havi' openings on Ihe boi'der n\' ihe lids ah»ng among ihe e\e- 
 j.-ishes. They seefele ;in oil\ subslauee: which servi-s to lubri- 
 cate IJH' con iuncli\ al sae. 
 
Conjuncti' 
 
 Meibomian gland in tarsal 
 plate 
 
 n 
 
 ->{\^ (J ^^ Tendon of levator palpebrse 
 
 f^^T!v~;^5? snperioris 
 
 Skin 
 
 Orbicularis palpebrarum 
 
 Ejelashes 
 
 Showing the Structure of the Upper Lid. 
 
Ketciium's Lessons on the Eve 37 
 
 The Conjunctiva is a thin mucous mcinbrano which Ijcgins 
 at the edges of the lids, lines them and folds back upon the 
 sclera (to which it is loosely attached) and covers the front of 
 the eye to the margin of the cornea. The part lining the lids 
 is called the palpebral conjunctiva; where it folds back upon 
 the eyel)nll it is caHed tlic fornix (arch) ; and that part which 
 covers the sclera in front is the ocular conjunctiva. 
 
38 
 
 Ki:t(.' hum's Lessons on the Eye 
 
 LESSON FOUR. (Section Two.) 
 
 THE MUSCLES OF THE EYELIDS AND EYEBROWS. 
 
 Occipito-froiitalis 1 
 
 Oi'biciilaris i)alpel)rainiiii I j^n supplied by the seventh nerve, 
 
 Tensor-tarsi j' 
 
 Tendo oculi i 
 
 Corriig'ator sui)ereilii ^ 
 
 ilso called facial nerve. 
 
 Levator ])alp('1)ra su])('iio]'is (in part). Tliii'd nerve. 
 
 The occipito-frontalis is the forehead muscle. It elevates 
 tlie (\yehro\vs and ])i()dnees Avrinkliiig of the forehead. 
 
 /'iffc , 
 i Ik 
 
 ^ 
 
 
 E. p. L. 
 
 Orbiculari.s palpebrarum. — The palpebral and orbital portions are 
 easily recognixed, though the line of separation is not always to be 
 seen. ('. S. i)oiiits to the corrugator supercilii: h. V. L.. iiit«M-nal i^al- 
 I)ebral llKanient : !•:. I'. 1... iiosition of external palprhral li.uanient. 
 (After Henle.) 
 
Ketciium's Lessons on the Eve 39 
 
 The orbicularis palpebrarum, (sphincter oculi) is the chief 
 muscle of the lids and is a powei'fnl volunt;ii\v spliincter, con- 
 sisting of an orbital, palpebral and lachrymal portion. It is 
 a thin. Hat muscle which lies immediately under the skin, en- 
 circling the eye and has fibres ])rjinching out connecting it 
 with the brow, forehead and cheek. By its action the lids may 
 be j)artially or gently closed or they nmy be tightly squeezed 
 together. 
 
 The tensor-tarsi or Horner's muscle is a thin muscular sheet 
 situated at the inner angle of the orbit behind the lachrymal 
 sac. This muscle is really a deep portion of the orbicularis 
 palpebrarum. Tt divides the two portions Avhich cover the 
 posterior ])art of each canaliculus. \n front of the lachrymal 
 sac is the tendo oculi, a short tendon about G mm. long and 
 can be felt as a little ridge by pressing the finger against the 
 side of the nose at the inner canthus. The tensor-tarsi and the 
 tendo oculi both serve to empty the lachrymal sac by involun- 
 tary compression, thereby forcing its contents down through 
 the nasal duct and from there into the nose. 
 
 The corrugator supercilii is a short ribbon-shaped muscle 
 located at the upper ridge of the frontal bone at about the 
 middle of the eyebrow. Its action is to draw the middle of 
 the eyebrow inwards and downwards which gives the froAVJi- 
 ing aspect to the face. 
 
 The levator palpebra superioris acts in opposition to the 
 orbicularis and elevates the uppei' lid. It has been mentioned 
 in connection with the intra orbital muscles as it lies entirely 
 within the orbit. 
 
40 Ki:iciiim's Lf.ssoxs on tiik Eve 
 
 QUIZ ON LESSON FOUR. 
 
 1. AVlial is tlic niiatoinical name foi' eyelid? 
 
 2. Locate tlie ])ali)el)fal fissure. State wliat it reefers to. 
 
 3. AVhat is meant by outer eantlius and iuiu'r eaiitluis.' 
 
 4. State just exactly Avluit constitutes tlie conjunctival sac. 
 
 5. Make a diagram showing in tlie ])ro])ci' ])osition, the 
 
 puncta, caruncle and the half nu)on fold. 
 
 G. "What does the plica semilunaris represent.' 
 
 7. AVhich A\ay do the (\velashes turn in each lid? 
 
 8. Name the layers of the lid fi'om tlie skin inward. 
 
 9. AVliich layer gives form to the lids? 
 
 10. TTow many meibomian glands in each lid and what is 
 
 their function ? "What sei)a rates them from the eyeball ? 
 
 11. Describe the conjunctiva ; the fornix. 
 
 12. Locate the iial|)ebral conjunctiva; ocular conjunctiva. 
 
 13. Name lln^ ])i-incipal muscles of llie lids and eyebrows. 
 
 14. Where do A\'e lind the orbicularis ])ali)ebrai'um ? What 
 
 nerve coni racis it ? 
 
 1."). Just wliere is tlie 1 ensoi'-tai'si and tendo oenli relatix'e to 
 the lachrymal sac' Whal aic they for.' 
 
 If). Where is the corinigator supercilii and what is its action.' 
 
Ketch um's Lessons ox the Eve 41 
 
 LESSON FIVE. 
 
 THE LACHRYMAL (Lacrimal) APPARATUS. 
 
 This refers to the secretion of "tears" and of their disposal, 
 and is divided into a 
 Secretory portion and an 
 
 Excretory portion. The former consists principally of the 
 lachrymal oland ; but as a matter of fact, the moisture that 
 commonly cleanses the ocular and conjunctival surface comes 
 from the mucous follicles of the palpebral conjunctiva, while 
 more copious supplies of tears are furnished by the lacliryiual 
 gland. Patients often complain of dryness of the eye, the lid 
 seems to stick to the ball. This is the result of the conjunc- 
 tiva being affected so that the normal secretion is somewhat 
 lessened. There are 
 two lobes to the gland; an 
 
 upper lobe oval in shape, about 20 to 25 mm. in length and 
 12 to 14 mm. in thickness. (See cut showing apparatus of 
 right eye). The 
 
 lower lobe is smaller and is sometimes called the 
 accessory gland. The gland is located at the base of the orbit 
 at about the 
 
 superior external angle, lodged in a depression of the frontal 
 bone to Avhich it is attached by loose connective tissue; the 
 under surface rests upon the eyeball at the 
 fornix (or fold of the conjunctiva where it turns from the 
 upper lid back upon the eyeball). 
 
 A study of the pictue Avill show the general plan of the 
 entire apparatus. From the gland Avill be seen several little 
 tubes — about ten — Avhich connect the gland with the surface 
 of the eyeball through the thin tissue between them and it is 
 through these 
 
 Lachrymal ducts that the slightly alkaline fluid— the tears- 
 is sprayed onto the globe. 
 
42 Kktciu'm's Lessons ox the Eve 
 
 Tlio Excretory Part is located at the 
 inner canthus and consists of the parts that diain the tears off 
 into the nose. These parts are the 
 Puncta lachrymalis (hichi'vninl ])oint) ; 
 Canaliculus (canal) ])hiral, canaliculi; 
 Lachrymal sac ; 
 Nasal duct. 
 
 The puncta lachrymalis is a very small oix'iiiiiii' on tlie edge 
 of the lid connecting with the 
 
 canal about 7 or 8 mm. in lengtli whicli are directed toward 
 the nose where the upper canal and tlio lowrr one meet and 
 form a common canal that connects Avitli the laclirynial sac. 
 From here the drainage is downward through a connecting 
 tul)e, the 
 
 nasal duct Avliich is directly continuous witli the sac and leads 
 into the nose. 
 
 The tears are drawn into the sac from the inner canthus 
 where they settle in a little depression, th(^ 
 Lacus lachrymalis, by suction, the motor power ])eing sup- 
 ported l)y tlie 
 tensor-tarsi or 
 
 Horner's muscle, wliich consists of two ])ai-1s of about \2 iiiin. 
 long arranged so as to compress each caiiab wliieli they do 
 involuntarily, and very often, thus sucking tlie secretion 
 through the puncta. In excessive secretion of tears, as in 
 crying, there is, of course, an overflow u])on the cheeks. Tliis 
 is called 
 lachrymation. 
 
Ketchum's Lessons on the Eve 
 
 43 
 
 
 
 P..S 
 
 11 
 
 O g 
 
 2-1 
 
 S!>. 
 
 % >> 
 
 d <n 
 
 51 
 
 si 
 
 M 
 
 
 
44 Ki:tciiu.m's Lessons ox the Eye 
 
 The picture illustrates the meibomian jiiands as well as the 
 lachrymal apparatus. Near the lachrymal gland will be seen 
 ») or 7 little spots which ai'e to show where and how the 
 tears i>t't from the gland through the conjunctiva onto the 
 eyeball. Just h(Me the picture is somewhat misleading, as 
 the conjunctiva is made to appear to be on the outside, or 
 external to the meibomian glands instead of inside next to the 
 eyeball. 
 
 The little dots along the edges of the lids are to represent 
 the ordinarily invisible opening — meibomian follicles — at the 
 ends of the meibomian glands through which an impercepti- 
 ble oily secretion passes to lubricate the conjunctival sac, thus 
 permitting the eve to move about without friction with the 
 lids. 
 
 QUIZ ON LESSON FIVE. 
 
 1. AVhat is meant by the term "lachrymal apparatus"? Give 
 
 its divisions. 
 
 2. AVhy do people complain of dryness of the eye? 
 
 3. Describe the jjosition of the tAvo lobes of the laehi'ymal 
 
 gland. 
 
 4. How and through what medium does the secretion from 
 
 the gland get onto the eyeball? 
 
 5. Diagram and name each part of the excretory apparatus. 
 
 6. How is drainage affected? (See Tensor Tarsi and Tendo 
 
 Oculi, lesson 4). 
 
 7. Do the meibomian glands ])c:w nii\' rrlntionship lo 1lic 
 
 lachrymal a])i)aratus .' If so, how.' If not. wli\' not.' 
 S. Where do mc fiml 1lie laeus laclir\ mails .' 
 0. What is tJH' ])lnral for eanalicnlus .' 
 10. Define laelirymation. 
 
 Note to the Student. — You have now learned a greal deal 
 about the ey(> just fi'om Ibese few lessons. Xow lake anxone 
 of the ]netures and 1all< lo it ;ind llieti show it to sonuMtne else, 
 telling liim what eaeii !)art is and what it is for and how it 
 coniH'ets u)) with some other ])ait. ele. 
 
Ketchum's Lessons on the Eve 45 
 
 PART TWO. 
 
 Part One covers the anatomy of the orbit, the 
 eye, and its appendages in a general way so that 
 the student can get a fairly complete conception 
 as a whole of Avhat is expected of him to master. 
 However, there are some essentials that he should 
 know, as well, that are not found in any text on 
 the eye, and would require some research to cover. 
 These will he found fairly well presented in Part 
 Two. 
 
46 Ki:tciil'm's Lessons ox tjik Eve 
 
 PART TWO. 
 
 GROSS DESCRIPTIVE ANATOMY AND PHYSIOLOGY 
 OF THE EYE. 
 
 THE SCLEROTIC. 
 
 This is sometimes called the Sclera or the white of the eye 
 and is an opaque fibrous membrane covering five-sixths of 
 the entire eyeball. In old age it sometimes becomes a dnll 
 yellowish hue, due to infiltration of fat, especially near the 
 margin of the cornea. Its greatest thickness is found at the 
 back part around the optic nerve where it is about one mm. 
 From this region forward it grows thinner until it is from 
 four-tenths to six-tenths of a unn. only. AVhere the sclera 
 and cnniea come together is called the 
 sclero-corneal margin. 
 
 It is scantily supplied with blood-vessels and consequently 
 gets its nourishment from its own lymphatic canals with 
 ■which it is abundantly supplied. Its nerves are derived from 
 the ciliary nerves. 
 
 THE CORNEA. 
 
 The cornea is legaidcd as the fi'oiit window lo tlu' eye 
 and as an object glass of the ocular camera it is one of the 
 most important portions of the apparatus. Being necessarily 
 placed at the front, and exposed whenever llic eyelids are 
 parted, it is more frequently injured than any oilier pail of 
 the eye. It comprises one-sixth of tlie external lunie or eoat 
 of the eye and its essential features are as folknvs: 
 
 It lias five layers: 
 
 ( 1 ) Epithelium. 
 
 (2) Bowman's membrane, or Anterior elastie lamina. 
 
 (3) True corneal tissue (Cornea Propria) which is the 
 center la\-er ami iiiueh thicker than aii> ol' the others. 
 
 (4) Descemets membrane or Postei-ior elastic lamina. 
 
 (5) Endothelium. 
 
Ketchu-m's Lessons on the Eve 47 
 
 Diameter — Vertical 11 mm.; horizontal 12 mm. 
 
 Refractive power — al)out 42 dioptres. 
 
 Radius of curvature — 7.8 mm. horizontal meridian and 7.7 
 in the vertical. 
 
 Index of refraction — ^1.33. 
 
 Blood vessels — none. 
 
 Nerves— highly sensitive— 60 to 80 branches of the anterior 
 ciliary nerves enter the cornea. 
 
 The cornea attains its permanent dimensions very early in 
 life and varies but little after the third year. It developes 
 faster than the rest of the eye. 
 
 Nutrition — As the cornea has no blood vessels from which to 
 get nutrition and grossly speaking is a network of cells, it 
 maintains itself upon the vital force of these cells, causing 
 an inter cellular flow of lymph Avhich remains al)out equal 
 during life. 
 
 Some interesting experiments have been made to deter- 
 mine the behavior of the cornea with regard to the rays of 
 the invisible portions of the spectrum. Its power of absorp- 
 tion of the infra-red or heat rays is a little superior to that 
 of water, but not notably so. The chemical or ultra-violet 
 rays also appear to pass through the cornea without sensible 
 diminution. 
 
 ARCUS SENILIS. 
 
 In elderly persons there is often seen a narrow gray crcs- 
 entric line either around the cornea or at its upper border. 
 This is called arcus senilis, or the arch of old age. It never 
 interferes with the vision, although it may extend some dis- 
 tance toward the center. It is occasionally seen in young 
 people, but is usually not seen before fifty or sixty years of 
 age, owing to decrease in nutrition with advancing years. 
 
48 Ki:t( II i.m's Lessons ox the Eyi-: 
 
 THE IRIS. 
 
 The iris is ;i colored iiieni])i-aiie, circular in fonii, liaii^iuii 
 beliind tlie cofiiea directly in front of tlie lens and in contact 
 ■\vitli i1 and ])erfofated at about its center by an a])erliire 
 of varial)b' size called the pupil. 
 
 In iiew-boi'ii Avinte children the iris is almost always blue. 
 This is due to the fact that its piguicnt-cells do iu)t develop 
 until sometime after birth, the coloration not being complete 
 until after the second year. In Albinos the i)ignient is en- 
 tirely absent. The distribution of i^ignient varies great 1\' in 
 different individuals. 
 
 Diameter — K) to 12 mm. 
 
 Thickness — A mm. 
 
 Diameter of pupil ranges from 3 to (3 mm. 
 
 Blood supply — The blood vessels of the iris come from the 
 two branches of the Ophthalmic artery, known as tlie long 
 posterior ciliai'y ai-teries, also the antcn-ior ciliary arteries. 
 
 Nerve supply — The contraction of the ])n])il occurs by the 
 action of a branch of the third nei've uj)on a narrow mus- 
 cular band, called the 
 
 Sphincter pupillae which encircles its border; and dilation 
 occurs 1)\- relaxation of the sphincter and contraction of the 
 7'adiating niuscidar fibres called the 
 
 Dilator pupillae, which action is coid rolled by the symjm- 
 thetic nei'N'e. 
 
 The structure of the iris ])rcsents two chief layeis — the 
 iridial stroma or body ])i'o|)ei' and the piiiuicnt la\cr: these 
 include live subdaycrs - 
 
 1. Anterior endot lu'linm. 
 
 2. Anterior boiuidary layei'. 
 .'■?. A'ascular stroma layer. 
 
 4. I'ostei'ior limiting la\-er. 
 
 ."). I'i-mcnt layer. 
 
 'I'he vaseidar stroma la\cr. rormin- the bnik of the ii'is. 
 consists of loose connectixe tissne support inii the nnnu'i-ous 
 blood vessels and nei'Ncs which occu|)y this la\ei'. 
 
This picture is not of the eye itself, but is a diagram made to show 
 why the second coat is called the vascular coat. The word vascular 
 means tube or tubes. Blood vessels and nerves are tubes. The general 
 color of the choroid is brown, not blue. However, it is customary in 
 coloring anatomical pictures to show the arteries red because the blood 
 within them is bright red, while in the veins it is a much darker red, 
 and as seen through the skin presents a bluish tinge. For general 
 blood supply see "Ophthalmic Artery". 
 
Ki-:TciirM's Lkssoxs ox Tin-: Evi-: 49 
 
 THE CILIARY BODY. 
 
 The ciliary body is that portion of the second tunic direct- 
 ly back of the iris and extending l)ack to the choroid. It 
 consists of two parts — ciliary muscle and ciliary processes, 
 which foi'iu a sort of a ring around the margin of tlie h'ns. 
 The ciliary muscle being close to the sclera iiear the sclero- 
 corneal junction, while the processes are a little farther back 
 or uiuler. It is supplied by a branch of the thii'd iierve and 
 possesses the involuntary function of adjusting the convexity 
 of the lens — called accommodation. The ciliary muscle con- 
 tracts and pulls the ciliary processes forward toward the lens, 
 thus relaxing the tension on the suspensory ligament which 
 holds the lens; with the tension relaxed the pressure is re- 
 moved ott' the anterior surface of the lens which then as- 
 sumes a more convex condition, sufficient to keep images up- 
 on the retina at different distances at which the eye may be 
 directed. 
 
 The ciliary processes aie some seventy or eighty slight ir- 
 regular folds and are reallly the forward continuation of the 
 choroid and it is to tht'se that the suspensoi'y liganu'nt is 
 attached. They are the most vascular portion of the eye- 
 ball, principally composed of pigment and numerous blood 
 vessels and this body is the principal source of the aqueous 
 humor. 
 
50 Ki:tciii-m's Lessons ox the Eve 
 
 
 study this diagram carefully as it represents a cross section of an 
 eye cut through just back of the ciliary body and shows the relation of 
 one part to any other part of that region of the second coat as indi- 
 cated by lines. The student will disregard a. b. c. and d. and begin at 
 the w^hite spot in the center, the pupil. From the margin of the pupil 
 to the next ring is the iris. From this ring — the iris — the ciliary body 
 begins and extends backward toward the choroid about 6 mm. Close 
 to the iris you see what looks' like a round string of elongated l)eads 
 to illustrate the ciliary processes. The letter g. points to the corona 
 radiata, which means the iris setsi in a raised ring, and it is in this 
 ring that the lens belongs. In the study of the lens and in accommoda- 
 tion this picture should be kei)t in mind. 
 
 THE CHOROID. 
 
 The choroid is a dark l)ro\vii iiicinl)i-aiH' lyini>- l)c1\vecii llir 
 sclera and the retina and const itulcs the posterior two-lliirds 
 of this second coat or tnnic fiom the ciliary l)ody hack'. Il 
 is vei'y tliiii. varying fi'oiu .<)(i of a inni. in fiont lo alxnit 
 .1 of a 111 111. at the ])ack. H is also eallt'd llic vascular coat 
 because it consists mainly of hlood vessels wliick arc nniled 
 l)y delicate connective 1i,ssn(> containinti iiiiniei-ous pi^ineiiteil 
 cells. The arteries are llie shoi-t ciliary. Its ruiictioii lliioui-h 
 its vessels is cldelly 1o serve iniliilion to thf reliiia. \i1reons 
 and lens. It forms tlie daik coaliiiti- t)!' Ilic iiiterior of Ihe 
 e.vel)al] ami its (hii-k ])i^iiieii1 is nature's provision to modify 
 the intensity of liyht that enters llirouiih (he pupil. 
 
Ketciium's Lessons on the Eve 51 
 
 THE RETINA. 
 
 The retina is a very thin delicate membvano which con- 
 sists principally of an expansion of the optic nerve. It is the 
 inner coat or tunic and extends forward to the ciliary body 
 where its termination is called the ora serrata. From there 
 on, devoid of nerve fibres and much thinner, it is continued 
 on forAvard over the inner surface of the ciliary body and 
 posterior surface of the iris. In the living eye it is trans- 
 parent and of a purple red color ; after death it soon becomes 
 opaque. It is connected with the choroid at the entrance 
 of the optic nerve at the back and at the ora serrata in front, 
 otherwise it simply lies upon it, but is not attached to it. On 
 this account vision is often destroyed by detachment of the 
 retina from its position against the choroid. 
 
 The minute anatomy of the retina is very complicated. It 
 is the complete development of this part of the eye that is 
 especially necessary to good vision. Vibrations of light reach 
 it from "all directions in front of the eye, but its region of 
 most distinct vision is about 1 mm. to the temporal side 
 of the optic axis. This is called the macula lutea or yellow 
 spot which is slightly oval and approximately 2 mm. in its 
 great diameter which is horizontal. Near the center of the 
 yelloAv spot occurs a small depression knoAvn as fovea cen- 
 tralis or center of focus. From the fovea to the center of the 
 optic disc it is about 4 mm., the optic disc being about 1.5 mm. 
 in diameter. 
 
 The retina has ten layers in the order named from the 
 choroid inward. 
 
 1. Pigmentary layer. 6. Internal nuclear layer. 
 
 2. Layer of rods and cones. 7. Internal gi'anular layer. 
 
 3. External limiting mem- 8. Vascular layer. 
 
 brane. 
 
 0. I ibrous layer. 
 
 4. External nuclear layer. , ,. . . 
 
 10. Internal hmitnig mem- 
 
 5. External granular layer. brane. 
 
52 Kiyiciii'M's LiissoNS ox the Eye 
 
 The second layer is of tlic most interest because ui)oii its 
 pi'o])t'r ik'veloj)iiiciit depends the best visual acuity. At hiitli 
 +here are :i,;^(i(),0()() cones and about 180,000,000 rods in lliis 
 layer and it is upon the furtlier development of tlu' eye that 
 j>()od vision depends. Should anything interfere with the com- 
 plete groAvth of the retina to prevent development of the num- 
 ber of cones to the extent of about 7,000,000 the vision is never 
 perfect and cannot be made so with glasses. In the distribu- 
 tion of these cones it has been found by microscopical exam- 
 ination that from the ora serrata back toward the macula they 
 gi-adually 1)ecome more numerous and closer together until 
 within the nuicuhi there are about 13,000 cones and no rods 
 at all. 
 
 The rods and cones are the terminal organs of the optic 
 nerve; receive vibrations of light which fall upon the retina 
 and connect these virbrations into impulses which are carried 
 by the different l)ranches of the optic nerves and tracts to the 
 brain ; here they pi'oduce the sensation of light. When an 
 image falls npon any otlier part of the retina tliere is indis- 
 tinct vision. 
 
Ki'yrciirM's Licssoxs ox 
 
 Kvr. 
 
 53 
 
 A, A cone and two rods 
 from the human retina 
 (modified from Max 
 Schultze) ; B, Outer 
 part of rod separated 
 into discs. 
 
 Meinbraua liiuitans interna 
 
 Diagramatic Section of the Human 
 Retina (modified from Schultze). 
 
 Surface view of retina, showing disposition and relative number of 
 the rods and cones. (Kolliker.) 1, from the fovea — only cones: 2, from 
 the margin of the macula lutea: 3, from midway between the fovea and 
 the ora serrata; a, profile of larger inner segment; b, of smaller outer 
 segment: c, rod. 
 
54 Kktchum's Lessons on the Eye 
 
 THE OPTIC NERVE. 
 
 T\\v optic nerve is iciiardcd as pai't of the l)raiii, and is de- 
 visable into tlut'c portions, cranial, orbital and ocular portions. 
 It is about 50 mm. long fi'oni the eye to the opiic connuissure 
 (also called the optic chiasm), wbere it meets the optic nerve 
 coming from the other eye. It is :U) nun. in llic oibit. 1(» mm. 
 in the optic canal at the apex of the ori)il and 1() iniii. intra- 
 cranial (within the cranium or skull). Behind the commissure 
 the two optic nerves become the optic tract. The nerve is 
 al)out ,") nnu. across. It has the foi'ni of a moditied S as it 
 lies in the orbit, thus allowing the eyeball to move about with- 
 out tension on the nerve. 
 
 OPTIC DISC. 
 
 Optic Disc. Optic Nerve entrance. Optic papilla. Nerve 
 head. Blind spot. (Sometimes improperly called Torus Op- 
 ticus.) This is the termination of the optic nerve as it pierces 
 the eyeball and spreads out to form the inner layer of the retina 
 —the internal limiting mend.)rane. Nornuilly, the optic disc is 
 nearly circular in outline and is about 1.5 mm. in diameter. It 
 is located about 3.5 mm. to the nasal side and about 1 mm. above 
 1he line of fovea centralis. The optic axis of the eye being be- 
 tween these two points. It has a ])inkish tint and on careful ex- 
 amination, is seen to present differently colored zones. (1) A 
 central clear spot, which is the funnel-like depression from 
 which emerges the central retinal vessel. (2) A vascular zone 
 containing many capillaries. (3) A narrow light l)aiid. which is 
 the connective tissue ring. (4) Sui'rounding all, the <lai'k chor- 
 oidal zone. Its size as seen with the ophlhahnoscope, direct 
 method, in the emmetropic eye is said to be lifteeii times larger 
 than actual. In the hy|)er()i)ic eye it is comparatively smaller 
 and in myopia greater. Whoever ligured it out that the mag- 
 nitication" was fifteen times must have ovci'h)oked the actual 
 facts in the case, if the disc is 1..') mm. in size and we midli- 
 l)ly that with 15 we get a diauu'ler of 2'J.5 unii. oi' almost an 
 inch. Never x'el have I seen a disc look anywhere ueai' that 
 si/.i'. .\t most it appears to be alio\i1 17 mm. 
 
 PORUS OPTICUS. 
 
 I',, Ills opticus is the physiological excavation and passage 
 on Ihc nasal side of tlic optic disc wh.Mc the ivtiual vess.'ls 
 are seen. 
 
Ketciium's Lessons on the Eye 55 
 
 CAPSULE OF TENON 
 
 (Note — See "orbital fat") 
 
 Carefully study this, as, usually given in text books, it is 
 somewhat difficult to understand just what the capsule really 
 means. Look at the pictures shown here as you read this. 
 The Capsule of Tenon, also called oculo-orbital fascia, in- 
 sheathes all the organs Avhich pass through it and forms a 
 cup for the eyeball, is continuous with the sheath of the optic 
 nerve and also forms a secondary attachment for the ocular 
 muscles. It is a delicate opaque membrane. AVhile it appears 
 as a part of the eyeball, it is not, as there is a lymph space 
 between it and the sclerotic which it covers to within 3 mm. 
 of the sclero-corneal margin where it fuses Avith the ocular 
 conjunctiva Avhich covers it. It is taught by common consent 
 that Tenon's Capsule is a socket in which the eyeball rotates 
 Avithout change of position, (meaning the socket is immovable 
 and the ball moves about in it AA^hen the extrinsic muscles pull 
 in it in any direction). Anatomy shoAA's that this is out of 
 the question because the anterior part of the capsule is closely 
 attached to the sclera in front of the insertion of the recti 
 muscles close to the cornea, hence the two move tog-ether upon 
 the cushion of fat behind them. In looking at the picture it 
 Avill be seen that the fibrous tissue of the sheaths of the muscles 
 is continuous Avith that of the socket, the effect of AA'hich is 
 partly to steady the eyeball and to resist the backAvard pull 
 of the muscles. It Avill be understood that AA'hen upon operat- 
 ing for strabismus a muscle is cut entirely free from its in- 
 sertion, it cannot drop out of position, but retains its rela- 
 tionship Avith the other extrinsic muscles. 
 
 The Check Ligaments aid in this also. 
 
56 
 
 Ki/rciiiM's Li:sso.\s ox tiik Evi-: 
 
 CHECK LIGAMENTS 
 
 The check ligaments during partial contraction of the external 
 rectus muscle, the internal check ligament (1. C. L,. ) being in a state of 
 maximum relaxation, and the external (E. C. L.) somewhat stretched. 
 (:Motais.) 
 
 Diagram intended to show how, during full contraction of the 
 external rectus, the external check ligament (M C. L.) is stretched to 
 its maximum length, and the internal (I. C. J..) is slightly stretched 
 also. (Motais.) 
 
 Note. — It will be observed that as the eye is sthown turned to its 
 utmost there is no pull on the back part oif the ball by the optic nerve 
 because of the fact that the nerve is very flexible and of a modified 
 S sha])e, which admits free movement. Most pictures showing the optic 
 nerve make it appear to be practically straight, which is not true. 
 
 The depth of the orbit is 4.') mm., the eye-ball ii4 mm., sets in it 
 leaving 3 or 4 mm. at the base, thus from the back of the ball tO' the 
 optic foramen is only a little over 17 mm., and as there is :^.0 mm. of the 
 Clitic nerve in the orbital cavity from tlie eye-liall to the foramen, that 
 leaves over 10 mm. for rotation. 
 
study this plate carefully. 
 
 It shows how the entire eye-ball and the muscles as well as the 
 spaces between one muscle and another is enveloped in the same 
 membrane. At the ends of the muscles, where cut, it will be seen that 
 each one is completely enveloped; also how the eye-ball "sets in" the 
 so-called cup and that a little to the anterior of the middle of the ball 
 the membrane turns back on the inside of the muscle and continues to 
 envelope it (them) to its origin at the apex of the orbit. The lower 
 left Figure presents another aspect of the enveloping membrane. In 
 the lower right Figure another view directly from behind the eye, 
 forward, emphasizes the fact of the complete enveloping membrane 
 called The Capsule of Tenon. 
 
Ketchum's Lessons on ttte K\k 57 
 
 AQUEOUS HUMOR. 
 
 This is a thin clear alkaline fluid occupying- the anterior and 
 posterior chambers, and is supplied by the ciliary processes. 
 Its index of refraction is 1.33. In case of an injury or opera- 
 tion resulting in loss of aqueous the cavity refills in a few 
 moments. It does not seem hoAvever, that under ordinary 
 natural conditions a very i-apid secretion of the aqueous takes 
 place because its principal source of exit is through the spongy 
 tissue of the spaces of Fontana at the sclera-corneal margin 
 where it is drained off through the canal of Schlemm by the 
 anterior ciliary veins. To a lesser extent it also passes out by 
 the lymph-crypts of the iris. 
 
 The extraordinary solvent properties of the aqueous humor 
 makes it easily affected by drugs circulating in the blood. 
 Should the lens substance come in contact Avith it in small por- 
 tions at a time it completely dissolves it. It is by this method 
 that soft cataract in children is treated and the lens substance 
 is made to gradually disappear. 
 
 THE VITREOUS BODY OR HUMOR. 
 
 is a soft gelatinous, perfectly transpar-ent substance and occu- 
 pies the posterior cavity called the vitreous chamber also 
 hyaloid cavity. It has no special value in refraction excepting 
 its index of refraction which is 1.33. It is contained in a very 
 thin transparent capsule— the hyaloid membrane— which sep- 
 arates it from contact with the retina. It gets its nutrition 
 from the choroidal vessels. A certain amount of vitreous may 
 be removed without seriously injuring vision, and it seems to 
 be rapidly renewed from the ciliary processes through the 
 zonula ofzinn. The only well established exit of fluids from 
 the eye — the aqueous and vitreous — is that at the angle of the 
 anterior chamber. 
 
Ketchum's Lessoxs ox the Eye 
 
 THE LENS AND ITS CAPSULE. 
 
 Before birth Avhile gradual development of Ihe eye is taking 
 place, the lens is supplied with its nourishment by a vascular 
 membrane which surrounds and covers it. The vascular por- 
 tion of this membrane gradually disappears as the lens com- 
 pletes its development leaving it entirely clear and it there- 
 after serves as a capsule or complete cover for the lens and 
 ])i'ot('Cts it from the surrounding aqueous humor. 
 
 The lens is hohl in position by the suspensory ligament, also 
 called the zone of zinn and zonula of zinn, \\iiiel\ is tlir thick- 
 ened portion of the hyaloid membrane extending from the 
 ciliary body to the margin of the lens on its anterior surface. 
 
 This is the membrane that is affected by the ciliary muscle 
 when "accommodation" takes place. The lens is a biconvex 
 circular body, lying directly behind the iris and in contact 
 with it. The center of the anterior surface of the lens is its 
 anterior pole, and is about 2.3 mm. from the back of the 
 cornea and the center of the posterior surface is its posterior 
 pole which is about 15.6 mm. from the retina. It is a little 
 greater in convexity behind than in front. The central ])or- 
 tion of its anterior surface is opposite the pupil. Its posterior 
 convex surface lies against the hyaloid membrane iorming a 
 depression called the patellar fossa or hyaloid fossa. It is soft, 
 elastic and transparent and is alxtut S.T) nun. in its tiansverse 
 diameter and about 'SA mm. tliick at its least convexity and 
 4, at its greatest. 
 
 Radius of curvature. (Anterior) (PoslerioiO 
 
 At distant vision, h'ast eurxature 10 mm. (i mm. 
 
 At cldsest ^•isi()n greatest cuivatuie (• mm. 5..") nun. 
 
 l^.'fraetive ])o\vei' about 1(1 D. Index of refraetioii 1 }:!. 
 Xuti-itioii of the lens is su|)i)lie(l fniiii tiie ciliaiy body. 
 
Krc'i chum's Lessons on the Eve 
 
 59 
 
 ENLARGED DIAGRAM OF THE LENS 
 
 No. 1. 
 
 «;-a;^:: 
 
 .%. 
 
 
 - 
 
 -r 
 
 V 
 
 
 >- 
 
 s^'^ 
 
 ^ 
 
 No. 2 
 
 No. 3 
 
 No. 1 shows the sectional layers of the lens which is somewhat 
 similar to that of an onion, and opening up in its antero-posterior 
 diameter. 
 
 No. 2 shows the relative iiroportions and curviture of both surfaces 
 of the lens in its antero-posterioor diameter which is from 4 to 4.5 mm. 
 
 No. 3 shows the greatest diameter of the lens (al)out S..5 mm.) as 
 it is held in position directly back of the pupil. 
 
 The usual diagrams of the lens seen in l)ooks show it to appear 
 oblong and sharp on the edge. It must be remembered that such a 
 picture is made to represent the eyeball — a sphere — cut in half, thus 
 leaving a flat side view. The lens cut in two, vertically, would appear 
 oblong accordingly. Its edge is rounded— not sharp— and its surfaces 
 always spherical, as shown in No. 2. 
 
60 Ki:T(rirM"s Lkssoxs on ttte Eyi; 
 
 THE CANALS OF THE EYE 
 
 Petit 's Canal, Hyaloid Canal, Schlemm's Canal 
 
 The canal of Petit is a narrow channel which encircles the 
 niai'gin of the lens. It is filled with lymph (a fluid) which 
 conies from the ciliary \-essels and is sn])])()sod to su])ply nu- 
 trition to the lens. 
 
 The hyaloid canal, also called the canal of Stilling, canal of 
 Cloquet and Central canal, is a very fine line of space in the 
 vitreous hunioi' exteudino' from the lens hackward to the 
 retina. It cannot Ix^ seen when lookin«;' into the interior of 
 the vyo Avith the o])hthalmoscope. 
 
 The canal of Schlemm is located in the sclerotic close to the 
 margin of the cornea forming a sort of a i-ing arouml the front 
 part of the sclerotic. It is really a channel of small blood 
 vess(ds Avhich serve to cari'y oft" the debi'is of the eye l)ack into 
 the circulation. Directly where the iris aiul the cornea come 
 together around the margin are a numhei' of little openings 
 called the spaces of Fontana through which the Huid passes 
 from the anfei-ior chaiid)er in order to get into the canal of 
 Schlemm. AVhenevei' from disease or injury to the eye this 
 canal is closed, the drainage of the eve is practically destroyed 
 and the pei'son graduall\' becomes blind. 
 
Kktciium's Lessons ox the Evic 61 
 
 ORBITAL FAT. 
 
 The orbit is tilled Avith fat — adipose tissue — Avhich is bound- 
 ed in front by the capsule of Tenon and its fibrous expansions. 
 It is very delicate in structure and forms an almost fluid sup- 
 port for the eye, "well adapted for its movements in all direc- 
 tions without pressure. In operating- for removal of the en- 
 tire eyeball this fat is not disturbed, as the cutting is first 
 made directly around the margin of the cornea where the con- 
 junctiva and capsule are both dissected clear from the scler- 
 otic and continued on to the insertion of the recti mnscles 
 when each one is raised with a hook and cut close to the 
 sclera. The blunt pointed curved scissors continue to follow 
 close to the sclera separating all tissue until the optic nerve 
 is reached and cut, when the entire eyeball is then removed 
 from the pocket or inside of the capsule. The muscles, the 
 fascia and the fat have not directly been disturbed and of 
 course retain their usual relationship and together form a 
 basis for the use in Avearing an artificial eye. 
 
 CIRCLET OF ZINN— LIGAMENT OF ZINN— ZONE OR 
 ZONULA OF ZINN— TENDON OF ZINN 
 
 The circlet of zinn is the vascular circle around the optic 
 nerve foi'ined from tAvigs of the short posterior ciliary arteries. 
 
 The ligament of zinn is the loAver part of the common tendon 
 that encircles the optic foramen at the origin of the recti 
 muscles and must not be confounded Avith the zone of zinn or 
 zonula of zinn, Avhich are other names for the suspensory liga- 
 ment around the lens. 
 
 LIGAMENTUM PECTINATUM IRIDIS. 
 
 The ligamentum pectinatum iridis consists of a mass of 
 spongy tissue and occupies the angle of the anterior chamber 
 Avhere it unites the iris and the ciliary muscle at the inner 
 corneal bordin-. It is intimately connected with the spaces of 
 Fontana. 
 
62 KRTcrir.M's Li^ssoxs ox the Eve 
 
 BLOOD SUPPLY. 
 
 The ophthalmic artery lias been mentioned as a branch of 
 llii' internal carotid artery. These two pictiues will serve to 
 show 1lic principal blood sii])])ly of the bead. It is called 
 The Carotid System of Arteries. 
 
 These arteries aie found on either side of the neck on about 
 a vertical line with the ear. There is a main stem callecl the 
 Common Carotid. 
 
 At a i^oint just back of the loAver jaw bone it separates into 
 t\\'o branches which are nanuHl 
 The External Carotid and 
 The Internal Carotid. 
 
 Each of these a!t»ain form several l)ranches Avhicli have iianies 
 according to the local parts they supply. The external is dis- 
 tributed about the external part of the neck and head while 
 the internal is contined almo.st entirely to the contents of the 
 cranial cavity. One other blood sujjply of the brain comes 
 from the Vertebral arteries. It will be observed in the picture 
 that the ophthalmic ailery bi-anches off from the carotid close 
 to the a])ex of Ihe orbit just back of the optic foramen and 
 from there )>asses llii-ouiih the foramen along Avith the optic 
 nerve into tiie orbit where it continues forward under the 
 lower border of the superior obli(iue and its i^ulley — trochlea — 
 to th(> ])ase of the orl)it where it terminates in two bi'anch(>s. 
 Altogethei' the o])!)! ha I ni ic ar1er\ ihe Iruiik loses itself into 
 ten separate branches and thus serves 1o sujjplx' iiuli\idual 
 l)arts of the conlenis of the oibital cavity. 
 
Showing location of the Cartoid arteries and where the Internal 
 l)ranches off and passes back underneath the ear and up into the skull. 
 
This picture is to show the connection of the Ouhthalmic artery 
 rith the Internal Cartoid artery. 
 
SupTaorbilal artery 
 
 LACHRYMAL GLAND 
 
 Superior rectus, cut 
 
 EYEBALl 
 
 External rectus 
 
 Lachrymal artery 
 
 Superior rectus, cut 
 Inferior ophthalmic lein 
 Superior ophthalmic leiu 
 
 OPTIC XER IX 
 
 Common ophthalmic vein 
 
 Commencement of superior 
 ophthalmic vein 
 
 Reflected tendon of superior 
 
 oblique 
 Ophthalmic artery 
 
 Anterior ethmoidal artery 
 
 fjiij- — Posterior ethmoidal artery 
 Ciliary arteries 
 Levator palpebrae, cut 
 Ligament of Zinn 
 Ophthalmic artery 
 
 OPTIC COMMISSURE 
 
 Internal carotid artery 
 
Ketc hum's Lessons on the Eye 63 
 
 THE VEINS OF THE ORBIT 
 
 It will be remembered that the ophthalmic artery carries the 
 l)lood into the orbit from the brain through the optic foramen. 
 (See red vessels in the picture.) At the base of the orbit 
 (in front) it finds its way into the veins (see blue vessels in 
 cut) which gradually enlarge as they go l)ack towai'd the apex 
 until they form two main trunks— the superior ophthalmic vein 
 and inferior ophthalmic vein which togethoi' at tlie apex form 
 one single and larger vein — the common ophthalmic vein and 
 from here passes into an opening called the cavernous sinus. 
 
 The branches of these veins are 
 
 (1) The superior muscular branches. 
 
 (2) The ciliary veins. 
 
 (3) The anterior and posterior ethmoidal veins. 
 
 (4) The lachrymal vein. 
 
 (5) The central vein of the retina. 
 
64 
 
 Ki-rrciirM's Li:.s.^o.\s o.x nij-: Eve 
 
 THE EXTRINSIC MUSCLES. 
 
 liesides the oi'diiiary text on tlieso muscles there are sevei'al 
 points that a rei'ractionist should know. For extended read- 
 inp: involving- every progressive thought of today on the action 
 of these muscles the reader is referred to the two large volumes 
 on "The ]\[uscles of the Eye" by Lucien B. Howe, ]\r. 1)., of 
 Buffalo; also a single volume, "IMotor Apjiai'atus of the lOyo." 
 by George T. Stevens, M. D., of New Yoik. Other h.x.ks of 
 minor value are of course on the mai-ket. 
 
 Not usually mentioned in connection A\ith tin- extrinsic 
 muscles there are check lig-aments (ligamentous aileious — or- 
 bital tendons) that should receive attention. 
 
 These names are given to small fibrous bands that connect 
 each extrinsic muscle close to its insertion on the globe, to sur- 
 rounding parts. The,v serve to modify any extienu' action of 
 the muscle j)roper, acting as bands of restraint as wh'II as aid 
 in harmonious action of two or more of the muscles and are 
 an aid to i)erfect binocular fixation. See '• Capsule of Tenon." 
 Ill regard to the exact distance from the sclero-corneal margin 
 the four recti muscles have their respective insertions, there is 
 some little differoice of measurements given b\- the authors 
 because nature varies, but a fair average in detail is as t'ollows: 
 
 
 Length 
 
 Width at 
 
 Insertion 
 
 on Schlera 
 
 Distance 
 
 from 
 
 Cornea 
 
 Relative 
 Power 
 
 
 41 mm. 
 40.6 mm. 
 40 mm. 
 41.8 mm. 
 
 10.75 mm. 
 10.75 mm. 
 13 mm. 
 la mm. 
 
 G mm. 
 7 mm. 
 
 7 mm. 
 
 8 mm. 
 
 Stroiijiest 
 '2d stiongost 
 'Ad stroujifOSt 
 
 Hxtcnial Kt'dtus 
 
 Superior Rectus 
 
 Weakest 
 
 
 
 ^'<.nr allenlion is now drawn lo tlie WIDTH of ihe insertion 
 of the muscles or rather the tendinons poiMion, in front, of 
 each recti muscle of from 10 to IM mm. Xow added together 
 the total distance around the e\.'-l)all co\cr<'d l)\ the inseilion 
 of these fom- muscles is ahout Iti mm. As the eye!. all at 
 its e(|uat()i' is alioul 2M mm. that gi\cs its gi'eatest cireum- 
 eference say 70 mm. The a ntero-post eri(U' diameter i)eing 
 ahout 24 mm., we now TukI that the insertion of these muscles 
 
Ketc hum's Lessons on the Eve 65 
 
 being in front of the equator are at a point Avhere the ciicuni- 
 ference is somewhat loss — say 62 mm. This knids you to the 
 fact that the combined length of these insertions practically 
 make a complete band around the eye leaving only about 
 •4 nnn. between the margin of each insertion. From the in- 
 sertion backward these muscles diminish in width, swell again 
 at the center and become smaller again at their origin at the 
 apex of the orbit. 
 
 The reason we do not see these nuiscles at their insertion is 
 that they are covered first with the opaque capsule of Tenon 
 which covers the sclera to within 3 nun. of the sclero-cor)U'al 
 margin and over this on the outside is the ocular conjunctiva. 
 
 Whenever an operation for strabismus is necessary the sur- 
 geon must first make an incision through both the conjunctiva 
 and the capsule before he can get to the muscle. 
 
 Most of the pictures shown in the books are rather mislead- 
 ing in making the width of the insertion of the recti muscle 
 appear rather narrow. The proper physiological function of 
 the extrinsic muscles is to maintain fusion and therefore 
 stereoscopic vision at any and all distances. 
 
 Action. — No one of the muscles of the individual eye acts 
 singly, but in groups of two or more as shown in the following 
 table : 
 
 Upward Superior rectus and inferior ob- 
 lique 
 
 Downward Inferior rectus and superior ob- 
 lique 
 
 luAvard - Internal rectus and superior and 
 
 inferior oblique 
 
 Outward External rectus and superior and 
 
 inferior oblique 
 
 Upward and Inward Superior rectus, external rectus, 
 
 and inferior oblique 
 
 Upward and Outward Superior rectus, external rectus, 
 
 and inferior oblique 
 
 Downward and Imvard Inferior rectus, internal rectus, 
 
 and superior oblique 
 
 Downward and OutAvard Inferior rectus, external rectus, 
 
 and superior obliciue 
 
66 Ki-:tciiu.m's Lessons ox the Eve 
 
 THE REFRACTIVE MEDIA. 
 
 Ill oi'dor that an eye may sec (listiiiclly it is iiecessai'v that 
 the vibrations of light that come from ditferent distances out- 
 side of the eye be enaliled to reach the inside coat called the 
 retina. In doing' this they ])ass through tlie Iranspareiit ])()r- 
 tioiis viz.: cornea, aqueous humor, lens, vitreous humor. All 
 of these together act as one piece of mechanism and are called 
 the refractive media because the word refraction means to 
 change and adjust rays of light from one direction to another, 
 and so these four parts act as the medium for properly adjust- 
 ing the forms of light that enter the eye. 
 
 Aftei- extended study of what are considered to be normal 
 eyes a certain positive "valuation of adjustment" has been 
 given to this refractive media in terms of dioptres and is 
 called the dioptric pov^er of the eye. A Dioptre is the unit of 
 measurement for optical lenses. lD.=a focus of ])ara]l('l rays 
 at 1 metre from the lens; 2D.=y2M. focus. Now looking at it 
 another way we would say a lens that focuses at OI. is a ID. 
 lens; at y^M. a 2 D. lens; consequently after this manner the 
 dioptric power of the eye was figured out. 
 
 Tscliei'iiing in his " IMiysiologic Ojitics," ])age :U. gives the 
 dioptric \alue of 1h<' complete optic system of the eye to 
 
 l)e 58.:^^. 
 
 The cornea about 421). and the Umis KiD. The aipieous and 
 vitreous humors liaving but littb- vabie in the sum total. 
 Authoi's differ but littlr on tlirsc points so it is (|uit(> safe to 
 sav that aliont (iOD. is the dioptric i.owri' of the fully devel- 
 
Ketciium's Lessons on the Eye 67 
 
 A STUDY OF ACCOMMODATION. 
 
 Accommodation, in the study of the eye, means in effect, a 
 change in the arrangement of the rays of light after entering 
 the eye, so tliat whether close to, or at some distance away 
 from the eye, the object looked at must be kept "focused" 
 or sharply defined upon the retina. This change takes place 
 only in the lens, not by sliding backward and forward as in 
 adjusting a telescope ; but merely by changing the adjust- 
 ment of the lens from its least convexity and in this way in- 
 creasing or decreasing its dioptric power. 
 
 In the study of Ophthalmic Optics and the practice of 
 Optometry it becomes necessary for the student to realize the 
 importance of this subject. 
 
 Two special points are always to be considered: 
 
 (1) Conjugate foci; (2) Amplitude and range of accom- 
 modation. 
 
 A great deal of study has been given in an experimental 
 way as to just how^ the "Act of Accommodation" is accom- 
 plished and the most satisfactory and acceptable action of 
 the eye is as folloAvs : 
 
 (1) Parts concerned are — The lens and the suspensory 
 ligament and ciliary muscle Avhich directly surrounds it. 
 
 (2) Action — The contraction of the ciliary muscle nar- 
 rows the little space around the edge of the lens Avhich has 
 been held taut by the suspensory ligament which is attached 
 to it, thus releasing the tension on the lens, Avhich being some- 
 what elastic, increases in convexity according to the neces- 
 sity of regulating the light so that it focuses on the retina 
 properly. The relative distance the eye is from the object 
 desired to be seen is the governing influence impelled by the 
 brain to adjust it for that particular point. 
 
68 
 
 Ki:tc hum's Lkssoxs ox the Eve 
 
 According to scientific tests of many thousands of human 
 eyes as regards vision it is a fact that -wlien one is twenty 
 feet or more away from any object he is looking at that no 
 accommodation is necessary at any age, in the perfect eye, 
 in oi-der to see plainly. Here the eye is said to be at rest — 
 meaning no acconnnodation or eye strain. According to 
 th<' ''laAvs of light." however, at any age, the adjustment 
 (accommodation) becomes necessary Avhen looking at an 
 object at any point closer than twenty feet. The closer the 
 o])ject the greater the demand for th(> adjustment. This is 
 Avhat is termed conjugate foci in the sense that soim' one 
 ])oint outside of the eye is always in dii'i^ct focus with the 
 retina. 
 
 Range of Accommodation 
 
 We present here a tal)lo having reference to the fact that 
 "Accommodation," or the 230wer to adjust the lens, decreases 
 gradually as the years pass. 
 
 Amplitude 
 Year in Dioptres 
 
 Year 
 
 Amplitude 
 in Dioptres 
 
 ]0 
 
 15 
 
 90 
 
 14 
 
 12 
 
 10 
 
 8.5 
 
 7 
 
 5.5 
 
 4.5 
 
 45 
 
 50 
 
 55 
 
 3.5 
 
 2.5 
 
 1.75 
 
 25 
 
 30 
 
 35 
 
 40 
 
 60 
 
 65 
 
 70 
 
 75 
 
 1 
 
 0.75 
 
 0.25 
 
 0.00 
 
 
 Now ui)oii i-efereiice to the table it will be seen that as 
 the lens becomes harder and less elastic by age, it eventually 
 entirely loses this power and needs artificial hel]) in the form 
 of glasses that will supply the deficiency, in early youth. 
 then, we find that llie I'ange or adjustment of aeeoniuiodation 
 is the greatest, and that is why glasses become necessary for 
 feasy close w^ork at about forty-five years of age, and tluMv- 
 after an occasional change to a strong»f focus is lu'eded to 
 keep pace with the gradual loss within the eye. 
 
Kktciium's Lesson's ox the Ev 
 
 69 
 
 SHOWING CHANGES IN ACCOMMODATION 
 
 Ciliary muscle 
 
 Even though one may know the anatomy of the parts involved in 
 accommodation, still it is sometimes difficult to grasp just what does 
 take place. The two diagrams here shown will, serve to make it more 
 clearly understood. Remember, the diagrams are flat views and the 
 student must always have in mind that he is facing the front of the eye; 
 that the ciliary muscle and suspensory ligament surround the edge of 
 The lens; that the lens is at its least convexity as shown on the shaded 
 part of the one picture. Now, when the ciliary muscle contracts it 
 draws closer to the edge of the lens all around it equally. The lens 
 then becomes thicker through its antero-posterior diameter. At the 
 same time the pupil contracts a little to sharpen vision. A branch of 
 the third nerve affecting both the ciliary muscle and the sphincter 
 muscle of the iris act at the same time. Such a change is constantly 
 going on as a person changes his view from one point to another. 
 
Ki:r(iirM"s Lessons ox the Eve 
 
 A study of Accomraodation. 
 
 Change in the curvature of the lens in accommodation according 
 to the theory of Helmholtz. — (Modified from Landolt.) 
 
Ketchum's Lessons on the Eve 
 
 SPASM OF ACCOMMODATION. 
 
 This term represents the ''live wire" of the majority of 
 complaints that are classed under the condition called "eye- 
 strain." It is the fighting line between the oculist and the 
 optometrist. It is the home office of trouble for the refrac- 
 tionist who doesn't thoroughly vmderstand its little game of 
 deception. It is the thing that really put optometry on the 
 map Avhere it is today. It is the thing that demands lots of 
 respect and attention. Study it. 
 
 Getting doAvn to facts. Spasm of acconnnodation means a 
 tired ciliary muscle resulting from an excessive demand upon 
 it to adjust and maintain more perfect vision which it be- 
 comes necessary to do when some departure from normal 
 vision exists in the eye. A tired muscle cramps or contracts. 
 When the ciliary muscle is tired it manifests the fact by 
 causing distress in various ways. Knowing that contraction 
 of this muscle is what adjusts the focal power of the lens, 
 the student will at once realize that the nerve force used is 
 compelled to act beyond its normal capacity and must finally 
 become more or less inefficient. Such is the case with vary- 
 ing symptoms of this disorder. It being partial at times 
 called clonic spasm and again mor(> or less permanent called 
 tonic spasm. AVhen the oculist finds such a condition ap- 
 parently manifest he uses "drops" called a Cycloplegic which 
 releases the cramped condition of the ciliary mufccle and 
 enables him to get the exact refraction of the eye very 
 readily. Being a physician he is legally entitled to use drugs 
 according to his best judgment. The use of such drops has 
 its inconveniences and draw-backs. Necessity demanded a 
 different procedure that ultimately Avould attain the same 
 results. After years of experimenting Avith Ophthalmic 
 lenses a veiy satisfactory method has l)een developed called 
 the fogging^ system, also an entirely different method called 
 static and dynamic skiametry ot' retinoscopy. It is by the 
 use of these two methods that the ()])t(mieti'ist is able to com- 
 pete with the oculist and satisfy his patients. 
 
Kiii'c iu-m's Lkssoxs on the Eye 
 
 
 
 PART THREE 
 
 
 
 
 pfesciils ill 
 
 simpl 
 
 e form the sort 
 
 of p 
 
 ithologieal 
 
 conditions 
 
 of the 
 
 eye that any refractionist s 
 
 lould 
 
 l)e familiar 
 
 with. 
 
 The Optometris 
 
 t has 
 
 his li 
 
 mita- 
 
 tions and s 
 
 honld 
 
 al:)solutely know 
 
 them. 
 
 His 
 
 per- 
 
 sonal wolf; 
 
 re aiK 
 
 that of his patient must 
 
 it all 
 
 times be re 
 
 el\one( 
 
 Avitli. Let your 
 
 mott( 
 
 be ' 
 
 'Play 
 
 Safe." 
 
 
 
 
 
 
 Now til a 
 
 t you 
 
 ha\e become fa 
 
 miliar 
 
 witl 
 
 1 the 
 
 aiiatoniy, ]i 
 
 li ysioh 
 
 jiy and o])tics o 
 
 llie 
 
 '\ e i 
 
 will 
 
 ])r()ve an e 
 
 asy matter 1o aO(juire ; 
 
 11(1 li. 
 
 )1(1 a 
 
 tiood 
 
 working' k 
 
 lowled 
 
 ^f of diseased C( 
 
 ii(li1i( 
 
 
 
Ketchum's Lessons on the Eve 7Z 
 
 DISEASES OF THE EYE THE OPTOMETRIST SHOULD 
 RECOGNIZE 
 
 Every refractioiiist before taking the first step toward the 
 regular examination for glasses should look carefully for any 
 unusual sign or symptom of the eye bearing upon any past 
 or present condition that would be likely to interfere with 
 successful completion of his work. During the inspection he 
 should ask the patient if at any time he has had any diseased 
 condition of the eyes of a serious nature, as there might be 
 some internal disease that he should know about. 
 
 Any acute inflammatory condition, sometimes even with 
 apparently trivial symptoms may cause photophobia and 
 ciliary spasm and interfere materially Avith exact work. 
 
 The list given here is merely intended as a synopsis that 
 will convey a quick understanding of the conditions men- 
 tioned and lead to a text book on Eye Diseases for a more 
 complete knowledge. 
 
 EXTERNAL DISEASES 
 
 CONJUNCTIVITIS— The palpebral conjunctiva lines the 
 lids back to the fornix where it turns back upon the ball and 
 becomes the ocular conjunctiva from there forward to the 
 margin of the cornea. 
 
 Of course in all acute stages of diseased conditions one 
 can refract only those of more or less mild form, if at all. 
 
 Simple conjunctivitis is merely an irritable conjunctiva 
 Avhich occurs from many causes including eye strain. There 
 is no discharge of pus, but more or less increase of redness 
 especially of the inside of the lids. Photophobia. Even if 
 you fit glasses under such conditions the patient may return 
 to say they are not satisfactory, when the Avhole complaint 
 would really be caused by the condition of the lids. 
 
 TRACHO]\IA or GRANULATED LIDS.— This is chronic 
 inflammation of the conjunctiva — always photophol)ia — and 
 nearly always haziness of the upper third of the cornea, called 
 Pannus. You cannot refract satisfactorily. 
 
 PTERYGIUM — is a fan-shaped growth of the conjunctiva 
 extending from the inner canthus to the edge and sometimes 
 upon the nasal side of the cornea. It interferes with satis- 
 factory refraction and should be removed by operation. 
 
74 Kktchum's Lessons ox the Eve 
 
 PINGUECULA— is a small, fatty deposit in the sclera be- 
 tween the cornea and the inner canthus. It is not a disease, 
 no harm comes from it, leave it alone. 
 
 CIIALAZIOX — -Sub-acnte tumor of one or more of the 
 ]\reibomian Glands in either the upper or lower lid. Xo pain, 
 usually grows larger in time and interferes with good visual 
 acuity by jDressing on the eye-ball and distorting everything 
 seen. Cannot refract very satisfactorily on that account. 
 Advise operation. 
 
 liLEPIIARTTTS— Thickening of the edges of the lids by 
 inHammatory process or eye strain. Small scales at the roots 
 of the cilia and sometimes pimples, patients nearly always 
 astigmatic. Eefraction not always satisfactory until cured 
 by treatment. 
 
 HORDEOLUM — Common stye, very painful, often the re- 
 sult of eye strain. 
 
 EXTROPIOX— Edge of the lid turns in— is the result of 
 injury of chronic disease of the lids causing the cilia to rub 
 against the eye-ball. 
 
 ECTROPIOX — same cause as Entropion — edge of lid turns 
 away from the eye-ball. Usually the lower lid. This con- 
 dition results in epiphora. 
 
 EPIPHORA— is an overflow of tears upon the cheek be- 
 cause they cannot escape through the puncta into the lachrymal 
 canal on account of obstruction. 
 
 LACIIRYMATIOX— is a term used to denote an excessive 
 flow of tears from emotional causes. Xo ohst ruction. 
 
 \IOr>ULA — is an almost im|)ercei)til)le ha/iness of nil or a 
 small ])art of the cornea. 
 
 ^lACULA — is a small sjxd or ()])acit\' of Ihe cornea, usually 
 of the two anterior laxcis. 
 
 LEUCO^NIA — is a dense opacitx- of the cornea in ])nit or in 
 whole and usuall\- the r(>snlt of n sei-ious injury or disease 
 that alTeels the true corneal la\(M-. 
 
 PA.\.\rS- is a well deliiied ha/iness usually found in the 
 upper Ihii'd of tlm cornea, usually the result of Trachoma. 
 
Ketch u MS Lessons on the Eye 75 
 
 FOREIGN BODY IN THE EYE. (abbreviated F. B.) 
 
 This means anything at all that finds its way between the 
 lids and remains there, whether loose or attached. 
 
 Where this directly concerns the Optometrist is, that it 
 occurs very frequently that a person will call upon a refrac- 
 tionist anticipating- relief from some recent eye trouble and 
 demanding glasses for it. Inquiry discloses the fact that 
 within the past few days more or less irritation with some 
 pain has developed in one eye only. A well informed refrac- 
 tion ist must at once conclude that it is not a case of eye 
 strain. I^pon careful inspection in such cases under a good 
 light ])y oblique illumination a minute spot will be seen on 
 the cornea, that does not belong there. If gray in appear- 
 ance it is likely to be a small ulcer. If dark it is without 
 doubt some small particle that has become imbedded in the 
 anterior layers of the cornea and should be removed. In 
 either case don't touch it as it is a case for the medical doctor. 
 It is just as liable to occur soon after you have fitted that 
 person with glasses and if so you will be the first person 
 thought of and the blame given to you, so ])e careful to watch 
 out accordingly. 
 
 CORNEAL ULCER. 
 
 Very painful, photophobia intense, lachrymation profuse, 
 palpebral and ocular conjunctiva inflamed. Inspection- will 
 show a small gray spot on the cornea. It must have imme- 
 diate and skillful attention, as if in front of the pupil it may 
 result in partial blindness in that eye. 
 
 PTOSIS — Drooping of the uj^per lid. Usually congenital 
 owing to incomplete development of the levator palpebrarum 
 muscle. Operation does no good. If acquired, it is usually 
 the result of acquired syphilis and means a partial paralysis 
 of the third cranial nerve. Consequently all that the third 
 nerve supplies is affected and we have cycloplegia-mydriasis 
 with the cornea turned down and toward the outer canthus 
 owing to the muscles being unable to hold it in the pi'imary 
 position and leaving it under the control of the external 
 rectus and superior oblique. 
 
 ECCHYMOSIS— ''Black eye," result of injury. 
 
 TRICHIASIS— "Wild Hairs" or eyelashes usually turning 
 in and rubbing upon the eye-ball causing much distress, oper- 
 ation necessary for relief. 
 
Ketciu'm's Lessons ox i iik Eve 
 
 INTERNAL DISEASES 
 
 IRITIS. 
 
 Acute Iritis is vei-y ])aiiiful. Four ])rinci|)al symptoms are: 
 pain, contracted pupil, iris looks dull, redness on the sclera 
 around the cornea. Usually caused by syphilis or rheu- 
 matism. If not promptly and properly treated and the pupil 
 widely dilated, the posterior surface of the iris becomes at- 
 tached to the l(Mis capsule. Once such a condition is estab- 
 lished called posterior synechia the result is that the pupil 
 Avill not react to lijiht and also the lens has lost its adjust- 
 ment for accommodation and becomes static. In such a con- 
 dition it is out of the question to satisfactorily refract such 
 an eye on account of havino- no Avay to adjust the focus. The 
 Avay to detect the extent of the adhesions is to have a physician 
 use a mydriatic. 
 
 Anterior synechia is a term applied where the front part 
 of the iris has beconu' attached to some part of the inside sur- 
 face of the cornea, the result of disease or injury. Such a 
 condition can plainly be seen. 
 
 OPTIC ATROPHY. 
 
 Tile sul)jce1i\-e symi)1oiiis are I'cduelioii in the aeuteness 
 of vision both as to color and form, Avith more or less dila- 
 tion of the pupil — (mydi-iasis). Complete blindness is the 
 usual i-e.sult of the pj'0}>i"ess of this diseas(\ Ilavino- studied 
 and become familiar with the appearance of the o]itic disc in 
 health the examiner will (juickly notice the loss of its ])inkish 
 zone as well as its minute vessels Avhich have disajipeared leav- 
 ing- the entire disc presenting' a dull white ai^jieaiance, Avhile 
 the blood vessels, es])ecially the arteries of the retina, are 
 much smaller than usual. Thr ball letains its normal tension 
 and the refractive media char. i1 is by this compai'ison that 
 it is easy to dislinyuish belwcen iilaueoma and oi)tic ati'o]ihy. 
 I1 eliicflv oeenrs in middle lil"e and llicic is really no sueeess- 
 fnl Ireaimrnt. 
 
Ketchum's Lessons on the Eye 17 
 
 EVERY REFRACTIONIST SHOULD KNOW SOMETHING 
 ABOUT CATARACT 
 
 CATARACT is any complete or partial opacity of the lens 
 or its capsule. There are three general terms that cover all 
 conditions : 
 
 Congenital, 
 
 Tranmatic, 
 
 Senile. 
 
 The term "congenital" implies present at birth. In many 
 children directly after birth is found more or less opacity of 
 the lens which condition will remain stationary throughout 
 the life of that person. A slight opacity admits light into the 
 eye and the actions of a child thus afflicted simulates myopia. 
 The only remedy is surgical. 
 
 TRAUMATIC CATARACT. The term ''traumatism" means 
 injury. Anyone at any age can be thus afflicted. A blow 
 directly upon the eye-ball will cause it. If the capsule is not 
 ruptured it will become a permanent opacity. If, however, 
 a small rupture of the capsule occurs permitting the lens sub- 
 stance to come into contact Avith the aqueous humor, the latter 
 gradually absorbs it, the debris being carried off through 
 Schlemm's canal. 
 
 SENILE CATARACT is comparatively common and likely 
 to develop in anyone. It usually appears after the age of 
 fifty. The real and direct cause in any given case is unknown 
 other than we know that some interference has taken place 
 wdth the nutrition of the lens usually supplied by the ciliary 
 processes and the lymph in Petit 's canal. Some cases are 
 traceable directly to some general disease such as Diabetes, 
 Bright 's Disease of the kidneys, Arterial disease, etc. 
 
 Symptoms. — There is no pain nor inflammatory condition 
 present. The first sign is usually diminished acuity of vision. 
 The patient complains of seeing spots on the object looked at. 
 The interference with vision gradually increases until finally 
 there is only mere perception of light. In almost every in- 
 stance only one eye is aft'ected at first and progresses to quite 
 an advanced stage before the other eye shows any symptoms 
 Avhatever. It is almost inevitable, however, that the fellow 
 eye will follow^ the same course in due time. The time re- 
 quired for full development is very uncertain. It may be very 
 slow or may ripen completely within a few months, or it may, 
 at a certain stage become stationary. 
 
78 Ketciium's Lessons ox the Eye 
 
 There are four stages of (Icvplopiuciil in senile cataract: 
 
 lncii)ioiit, 
 
 .M;i1iii-iiiti- s1a<rc, 
 
 .Mature or I'ipe, 
 
 Hyper-mature or ovei' ri])e. 
 
 The Incipient or l)e^inninji' condition is a more or less 
 ne])iilous — sliijhtly opa(|iie — dull appearauce of the lens in 
 which the patient feels rather than sees there is something 
 wrong. AVith a good light reflected by a retinoscope into the 
 eye it can be det(^cted l)y the observer, especially when com- 
 pared with the "reflex" of the othei- eye. Sometimes this 
 slightly opaque condition I'emains stationary foi- years, Avith 
 compai-ativcly lilllc loss of useful vision. Hence it is often 
 wise not to alaim the patient about if, but for your own pro- 
 tection an interested relative should be informed accordingly. 
 
 The maturing stage comes next. 
 
 The vision is becoming noticeably less acute as the oi)acity 
 increases. Swelling of the lens increases owing to absorbing 
 fluid between its layers. The patient, at this stage, requires 
 less plus for reading due to increased convexity of the lens 
 of the eye. The condition is popularly known as "second 
 sight" and sometimes, in (|uite an elderly person especially, 
 remains stationary for flic balance of his life. 
 
 The third stage means ripe cataract. The eye has become 
 blind owinii- to complete opacity of the lens, and its appear- 
 ance now is a dull ti'ray or slightly amber coloi'. It has lost 
 the lluid i)icvi()us]y absoi-bed. Hs many layei's have become 
 (irmly adhei'ed to one anoHier and it is at this period that it 
 is most easily se])a rated from its capsule and for best results 
 should l)e removed withoul much delay as furflnn- chanjues 
 ai-e likely to develop into Ihe hyper-mature slatie, and an 
 ()|)ei'afion upon over-ri]ie ealaracf is less fa\'oral)lc 
 diflieull Ihan durinti' 1li«' iiialuiv period. 
 
 more 
 
 AN APHAKIAL EYE 
 
 is an eyr willioul a Ims, usually Ihe rcsuH of an injury or 
 o])ei'ati()n. Sueli a couditioii can usually be delreled l>\ no- 
 ticing' llial Ihe pupil dips haekward instead of forward and 
 the iris is tremuhuis (if shakes as the eye is uH>\cd ahonl. 
 owiu'j 1o Ihe suppnri uf the leiis which was direetl\ behind 
 jiiid ill contact with it liaxinu heeii taken awa\. 
 
Ketchum's Lessons on the Eye 79 
 
 The usual spherical lens to correct infinity for an aphakial 
 eye is about a plus 10. Usually a plus cylinder against the 
 rule is required also. By no means is it usual to expect 
 good vision in such cases and it is considered excellent results 
 if fifty per cent vision is regained after a catai'act operation. 
 About plus three added to the distance lenses is lequired for 
 close Avork. 
 
 GLAUCOMA 
 
 This is an important and very serious disease of the eye 
 that every refractionist should be on the lookout for, espe- 
 cially in people somewhat advanced in years. When an eye 
 is once afflicted with this disease very little can be done for 
 it in the way of permanent relief. I can merely refer to it 
 in a general way and strongly urge the student to study it 
 carefully in some text book on diseases of the eye. The reason 
 why one should know how to detect it, is that in the majority 
 of cases in which it is developing it is found that the hereto- 
 fore acuity of vision of the patient is gradually becoming less 
 and he comes to you with all confidence expecting relief from 
 glasses. A relief Avhich, properly speaking, you cannot give 
 him. It ultimately means complete blindness with no prob- 
 able hope for a cure. If so, then can you not do as much for 
 the patient, with glasses, as can the Oculist? You can, of 
 course. But the Optometrist must always bear in mind that 
 he is not to be considered as ''the court of last resort" in a 
 legal or properly qualified sense and in no case should assume 
 any responsibility for suspected pathological conditions. 
 
 One special symptom to become familiar with is the "ten- 
 sion" of the eye-ball. First learn, by lightly pressing with 
 the forefinger of each hand upon the healthy eye-ball, its 
 "give and take" feeling. Glaucoma being a condition where 
 the drainage of the debris from the eye through the spaces 
 of Fontana and canal of Schlemm has become retarded, the 
 eye-ball gradually becomes more tense or hard until finally it 
 is a very easy matter to detect that fact by palpation with 
 the finger tips. 
 
80 I\i:Tcrir>r's T.r.ssoxs ox tiif. Eve 
 
 FLOATING SPOTS IN THE EYE 
 
 Very often the refractionist will have patients who com- 
 plain of the facl^ that "every once in awhile I have little spots, 
 like shadows, in my eyes and they appear to move around 
 when I move my eyes, but settle down and are quiet when I 
 am reading or writing. There isn't any pain about it but 
 they annoy me and I would like to know what is wrong." 
 This condition is knoAvn as 
 
 Muscae volitantes or floating particles in the vitreous. 
 
 You will state to the patient "that in most cases they do 
 not mean any harm as far as disease is concerned ; but are 
 usually the result of eye-strain, insomnia, indigestion, etc. 
 All of which must be looked after and remedied accordingly." 
 In myopia of high degree, floating specks are almost constant 
 and are not always relieved by Avearing glasses. 
 
 Having now given a general description of the principal 
 external and internal diseased condition of the eyes that it 
 is the duty of the Optometi-ist to recognize in order to "play 
 safe" l)oth to himself and his confiding patient, Ave leave this 
 thought with him : That no person is entirely his -own patient 
 who in any Avay is afflicted with even the slightest pathoK)g- 
 ical disturbance. An apparently simple symptom might and 
 often does lead to serious results if not promptly recognized 
 and cared for. A careless diagnosis with an ignorant prog- 
 nosis mav lend to troulile. Do not often advise nor assume 
 anv responsibilitv. KKFER THE CASE AT ONCE TO THE 
 OPHTHAl.lMOLOrilST. 
 
Ketciium's Lessons ox the Eve 81 
 
 NYSTAGMUS 
 
 Occasionally someone will call upon you to see if you 
 can benefit their vision with glasses. Upon the usual in- 
 spection (always necessary before proceeding with the Optical 
 examination) you discover a peculiar and constant lateral 
 twitching of both eyes. You have a case of genuine nystag- 
 mus. There are varieties of the movements classified under 
 this head ; but generally we find the movements or twitching 
 of the eyeballs are rhythmic bilateral and from side to side; 
 both to the right, then to the left, and so on, averaging in speed 
 from one to three times in a second and to the extent of about 
 two or three mm. to either side of the primary position straight 
 ahead. 
 
 This condition is usually congenital and with an obscure eti- 
 ology (cause.) Sometimes it is the result of some serious ejec- 
 tion of the eyes soon after birth, resulting in corneal scars that 
 prevent the "development of good vision. Congenital cataract 
 is also a contributing feature. When, however, the refractive 
 media is clear the condition of suspended development is 
 rather difficult to discover. Anyway, it's not your case, 
 because of the fact that it has been found that glasses offer 
 very little help in the way of improving vision. True nystag- 
 mus is not due to Optical' defect and is not traceable to occu- 
 pation. No perfectly satisfactory explanation of nystagmus 
 has yet been given, other than it is a perversion of the centres 
 for parallelism and not with the muscles themselves. 
 
82 Kktciium's Lessons ox the Eye 
 
 AMBLYOPIA 
 
 Strictly spcakiiio-, amblyopia is not disease in any form. 
 AVe classify it here because the text books do not explain the 
 term in a way to make it thoroughly understood by the non- 
 medical rafractionist. Its real meaning is as folloAvs, viz.: 
 Diminished visual acuity, congenital, Avith no possible remedy. 
 The eye is not blind nor diseased in any form. In no sense 
 is true amblyopia an acquired condition. The refractive 
 media is clear and may or may not be ametropic. Notwith- 
 standing correct retinoscopic findings, the glasses do not ma- 
 terially improve vision then or thereafter. The ametropia in 
 an amblyopic eye may be exactly the same as in the fellow 
 eye which sees perfectly with its correction by glasses, while 
 the former will not. The Ophthalmoscope or any other kind 
 of an objective examination shows nothing wrong. What is 
 the answer? Simply this: At one or more points from and 
 including the retina to and including the optic tract there is 
 an interference with the proper vibrations of light that have 
 reached the retina, and an undeveloped condition of some 
 unknown kind exists that obtunds detail in objects and gives 
 only a gross image in return. If for any reason the develop- 
 ment of rods and cones does not continue after birth the 
 vision remains accordingly. Microscopical study of the 
 retina shows about 8,500,000 cones in the I'etina at birth ; and 
 in the fully developed eye about 7,000,000. In the macula 
 alone, a space of less than 2 mm. in dianider. Iliere are in 
 tho developed eye 1;M)()0 eones. Tlow ]>lainl\- tlicn. is the fact 
 1lia1 in any condition wlicic llic eoncs arc less lliaii Ihe amount 
 re(|iiir(Ml foi- u'ood vision, 1 lie eye cannol he made subject to 
 decided iniprovemeiil. Also i1 must be renienib.Ted that the 
 optic ti'ael re|)i-esen1s a '•enlli\a1ed area"" thai is developed 
 only in aeeoi-danee willi llie demand made npon i1 llii-ongh 
 llie icfraelive media. 
 
 A diaunosis of aiiibl \ opia is made only by " exelnsion ; "' 
 meaning a llioroniib faniiliarily of all the ()])tical, i)liysiolog- 
 ical and pal liolotiieal conditions of the eye, and after eare- 
 
 fnllv- cxjimininu for all an.l eliniinaling tliem from the ease 
 we "li;iv<> onlv one i)rol);ddc condilion \r\'\ !lia1 in any way 
 
Ketch um's Lessons on the Eye 83 
 
 answers, so it must be amblyopia. Tlieie nw oIIht condii ions 
 of (liminish(Hl vision tliat simulate true amblyopia tluil in 
 our examination we find are false. They are classed as fol- 
 lows, viz. : 
 
 1. And)lyopia Exanopsia. 
 
 2. Amblyopia Toxic. 
 
 3. And)lyopia Hysterical. 
 
 No. 1 is diminished visual acuity, the direct result of un- 
 corrected ametropia ; and owing to want of o]itic tract train- 
 ing, does not immediately and fully respond to tlie coiTCct 
 glasses. If, hoAvever, the glasses ai-e woi'ii continually for 
 some time there is a gradual improvement in sight until after 
 a time it becomes comparatively normal. The history of the 
 case differs somewhat from true amblyopia as the element of 
 a high ametropia is ahvays present, and the vision improves 
 with glasses while in the true condition it does not. The point 
 is, be guarded in your prognosis. 
 
 Toxic amblyopia is diminished vision ahvays in both eyes, 
 the result of auto-intoxication of some form. It may be from 
 over indulgence in food, liquors, or drugs. Easily diagnosed; 
 and the remedy is to cleanse the system and put it into a 
 healthy condition after which the eyes will resume the same 
 vision as before. 
 
 Hysterical amblyopia is practically nothing at all the mat- 
 ter Avith the eyes. It is regarded by many as a sex problem 
 and treatment is directed toward the general nervous system. 
 In some cases it is of only short duration although it may 
 continue for several weeks. Judicious questions to the ])atient 
 will soon bring out the true condition. Leave it alone. 
 
84 Ki:'i(in:-M"s T.essoxs ox riir. F,vf. 
 
 PATHOLOGICAL VARIATIONS OF THE PUPIL 
 
 In ovovy case, before proceeding' with an examination for 
 glasses the eves should l)e carefully inspected for signs of 
 abnornuil conditions. This especially applies to the pupil as 
 more often than suspected it offers a very grave prognosis 
 at a time Avhen the affected person is little aware that any- 
 thing is seriously at fault with him. 
 
 Light reflex of the pupil means that under ordinary con- 
 ditions tlu^ pu])il will contract and dilate according to the 
 degree of light to Avhich the eye is exposed. Towards a bright 
 light it should contract and on turning away dilate more or 
 less. A fixed pupil never occurs in hoalth\- individuals with 
 healthy eyes. 
 
 AVhih^ over a dozen different terms are rec|uired in explana- 
 tion of ])upil reflexes, those given here arc the pi-ineipal ones: 
 
 1. Loss of Pui)illary light reflex with retention of the con- 
 verg(mce and accommodation. (This is Argyll-Eobertson 
 pupil.) 
 
 2. Loss of convergence and aeeoiiimodntion and I'etention 
 of light reflex (just o])i)osite to the Argyll-Robertson i)Ui)in. 
 
 8. TiOss of pu])illar\- rellex for light, also convergence and 
 accommodation (all Ihi'ee alfeeled). 
 
 4. Abnoi'iiial miosis (eontractio)i of the ]Mi])in wilh refen- 
 tion of light reflex and convergence. The miosis 1)eing eansed 
 eilhei' from abnormal sf iiiiulaf ion of 1lie spliincl er pupilhuN 
 (»r fi'om i);iialysis of the dilator pupillae. 
 
 5. Alinormal mydi'iasis fdilalioii^ witli rd eiit ion of con- 
 vergence and lighf I'cllcx. Slimulalioii ol' llie dilator ])U|)ilIae. 
 
 n. Anisocoria (dilTci-eiicc in size of pnpil). 
 
 7. h'regiilar form ol' pupils. 
 
 'I'll.- Ol f sprci.il iiileiesi 1o the re f fact ion ist is the 
 
 Argyll-Robertson iMipil (study it in the text hooks). 
 
Ketciium's Lessons on the Eve 85 
 
 Diagnosis. — Loss of the i)U])i]laiy li<iht rcilex, witli cither 
 contraction or nnnlinui dilation. IJotli exes aie similarly 
 affected in the greater number of cases, although, in some it 
 is unilateral for a long time. Again— the light retiex may be 
 utterly lost in one eye, and only partly lost in the other. This 
 light reflex is as a rule permanent, since it occurs the greater 
 number of times as an accompaniment of diseases of the 
 nervous system that are progressive, and it must be distinctly 
 remembered that it never occurs in healthy individuals. The 
 pupil is ahvays uniform and should never be confounded with 
 posterior synechia in any form, the latter being an attachment 
 of the iris to the lens capsule resulting from iritis. 
 
 Etiology. — While the general scientific opinion is that quite 
 all cases of Argyll-Robertson pupil are due to syphilis, there 
 are probable exceptions in a small per cent, but it is enough 
 to say that a most important symptom has been recognized 
 that leads to a grave 
 
 Prognosis. — Regardless of the apparent health of the 
 patient at the time of the examination. The fact that in this 
 condition the accommodation is not interfered with there will 
 be no trouble in refracting the eyes either for distant or near 
 point glasses, resulting in reasonable satisfaction. 
 
86 
 
 Kktciium's Lessons ox thf. Eye 
 
 OPTICAL NOMENCLATURE 
 
 (Reprint from the Keystone Magazine of Optometry.) 
 
 Address by Professor Frederick Before the Annual Convention 
 
 of the Michigan Association of Optometrists at 
 
 Jackson, Mich. 
 
 Every profession that treats on scientific problems makes use 
 of (fjlossaries) scientific technical names, for the purpose to 
 perfect a lang-uagv that may be universally understood. Op- 
 tometiy has such a language made up of words, roots, j^refixes 
 and affixes which are derived from the ({i-eek or Latin, and the 
 student who makes these derivatives a study can, with ease, 
 unravel the meaning of words or coml)ination of Avords, it mat- 
 ters not how comph'x or difficult they may appear. 
 
 For example, for "a-chroma-opsia," we look over the lesson 
 sheet, first column, for "a," Avhich signifies "lacking." Then 
 look for "chroma," which signifies color; then look for "op- 
 sia," which signifies vision; therefore, the term "a-chromat- 
 opsia," meaning lacking cohn- vision, in other words, color 
 blind. 
 
 Again, for the word an-irida we find "an" signifies lacking, 
 "irida" signifies iris — lacking iris. Let us now unravel the 
 com])ination of an-iso-coria : "An," lacking; "iso," equal; 
 "coi-ia," pupil. Lacking equal pupil. Anti-metr-opia: "Anti." 
 opposite; "metr," measure; "opia," error of Tefractioii. 
 Thei'cfore, antimeti'opia, o])posite measure of refraction, iiu^an- 
 iiig one eye nearsighted, the olhei' farsiglited. 
 
 WORDS, ROOTS, PREFIXES, AND AFFIXES 
 
 Words 
 A, An, 
 Aden 
 
 Amauro 
 
 Ambly 
 
 AntI 
 
 Aqueous 
 
 Argo 
 
 From 
 
 Greek 
 
 f'.reok 
 Clrcck 
 (Irook 
 batin 
 Greek 
 
 .Ml 
 
 iiiK 
 
 Prefi.xes, meanins "Lacking". (A-blepsia.) 
 
 (An-iso-metr-opia.) 
 Glands, such as tear glands. (Dacry-aden- 
 
 itis.) 
 To make dark (blind), (.\main-o-sis.') 
 Dull, dim. (Aml)ly-oi)ia.) 
 Opposite. (Anti-nietr-oi)ia.) 
 Water. (Aqueous Humor.) 
 Non-use, out of use. (Arg-ambly-opia.) 
 
Ketchum's Lessons ox the Eve 
 
 S7 
 
 Words From :\Ieaniiig 
 
 Amplitude Latin Fullness, completeness. (Amplitude of 
 
 Accommodation. ) 
 Algia Greek Pain or ache. (Neur-algia.) 
 
 Ab Latin Prefix meaning "Away" or "From". (Adduc- 
 
 tion.) 
 Ad Latin Prefix meaning "To" or "Toward". (Adduc- 
 
 tion.) 
 Blepharo Greek Eyelid. (Blephar-itis.) 
 
 Blenno Greek Mucus or pus. (Hlenno-rrhea.) 
 
 Brach Greek Short, near. (Brach-metr-opia.) 
 
 Blepsia Greek Vision. (A-blei)sia.) 
 
 Chroma 
 
 Core 
 
 Canthus 
 
 Cata 
 
 Cerat 1 
 
 Kerat ^ 
 
 Con 
 
 Copo 
 
 Cyst 
 
 Conus 
 
 Contra 
 
 Clonic 
 
 Greek Color. (A-chromat-opsia.) 
 
 Greek Pupil. (An-iso-corsia. ) 
 
 Greek Corner of the eye. (Inner Canthus.) 
 
 Greek Down or beneath. (Cata-phoria.) 
 
 Greek Cornea. (Ceratometer.) Proper Horn. 
 
 Latin Together with. (Convergence.) 
 
 Greek Strain, fatigue, worn out. (Copi-opia.) 
 
 Greek A sac. (Dacry-o-cyst-itis.) 
 
 Greek A cone. (Conic Cornea.) 
 
 Latin Opposite . (Contra generic.) 
 
 Greek Pertaining to confused motion. (Clonic 
 Spasm.) 
 
 Disc 
 
 Dys 
 
 Dexter 
 
 Dioptrics 
 
 Diopter 
 
 Dacry 
 
 Edema 
 
 Erration 
 
 Erythro 
 
 Ec, or Ek 
 
 Ectos 
 
 Eso 
 
 Em 
 
 Exo 
 
 Greek A round body. (Optic disc.) 
 
 Greek A prefix meaning "Bad". (Dys-opsia.) 
 
 Latin The right. (Oculus Dexter.) 
 
 Greek Science of refraction of light. 
 
 Greek A meter focus as used in Optometry. 
 
 Greek Tear. (Dacry-ops.) 
 
 Greek A swelling. 
 
 Latin Wandering. (Aberration.) 
 
 Greek Red. (Erythr-opsia.) 
 
 Greek Out. (Ec-tomy.) 
 
 Greek Outside. 
 
 Greek In. (Eso-phoria.) 
 
 Greek A prefix meaning "In". (Em-metr-opia.) 
 
 Greek Out. (Exo-tro])ia.) 
 
 Focus 
 Fundus 
 
 Latin 
 Latin 
 
 Coming to a point. 
 Foundation. 
 
 Graphy 
 
 Greek Description, drawing 
 
 Hydro 
 
 Greek 
 
 Hemi 
 
 Greek 
 
 Hetero 
 
 Greek 
 
 Hyper 
 
 Greek 
 
 Hypo 
 
 Greek 
 
 Water. 
 
 Half. (Hemi-an-opsia.) 
 Others, or many. (Hetero-phoria.) 
 Over, above. (Hyper-phoria.) 
 Under, or Ijeneath (Hypo-metr-opia.) 
 (My-opia.) 
 
Kktciium's Lessons on the Eye 
 
 Words 
 
 Itis 
 
 ISO 
 
 Image 
 I rid 
 
 Greek 
 Greek 
 Latin 
 Latin 
 
 Kinetic 
 
 Greek 
 
 Leuko 
 Lachrymal 
 
 Greek 
 Latin 
 
 Meter 
 Micro 
 Megalo 
 Mono 
 
 Greek 
 Greek 
 Greek 
 Greek 
 
 Nepho 
 
 Xeuro 
 
 Nyct 
 
 Nebula 
 
 Opia, Opsia, Ops. 
 
 Opia 
 
 Greek 
 Greek 
 Greek 
 Latin 
 
 Greek 
 
 Opsia 
 
 Greek 
 
 Ops 
 
 Greek 
 
 Ortho 
 
 Greek 
 
 Oculus 
 
 Latin 
 
 Oma 
 
 Greek 
 
 Photo 
 
 Greek 
 
 Phakia (phacia) 
 
 Greek 
 
 Plegia 
 
 Greek 
 
 Ptosis 
 
 Greek 
 
 Phobia 
 
 Greek 
 
 Punctus 
 
 Latin 
 
 I^seiido 
 
 Greek 
 
 Phoria 
 
 Greek 
 
 Pyo 
 
 
 Poly 
 
 Greek 
 
 Pali)ebral 
 
 Latin 
 
 Presby 
 
 Greek 
 
 Rhea 
 
 Greek 
 
 Retina 
 
 Latin 
 
 Spccli'iun 
 
 Latin 
 
 Spasm 
 
 ClriH'k 
 
 Senilis 
 
 Latin 
 
 Sthenic 
 
 Greek 
 
 .Meaning 
 
 Inflammation. ( Retin-itis.) 
 
 Equal. (Iso-coria.) 
 
 Resemblance. 
 
 Iris. Rainbow. (Irid-o-i)legia.) 
 
 :Motion, to move. 
 
 \Miite. (Leuk-oma.) 
 
 Pertaining to tears. (Lachrymal ducts.) 
 
 Meter or measure, f A-metropia.) 
 
 Small. (Micr-opsia.) 
 
 Large. (Megal-scope.) 
 
 One or single. (Mon-ocular.) 
 
 Cloud. (Neph-a-blepsia.) 
 
 Nerve. (Neur-a-sthenia.) 
 
 Night. (Nyctal-opia.) 
 
 Cloud, mist. 
 
 Affixes. 
 
 When applied to a word or a combination of 
 words, gives it the meaning of "An error 
 of refraction vision which may be cor- 
 rected by glasses", as Hyperopia, Myopia, 
 Presbyopia. 
 
 When ap])lied to a, word means "Vision". 
 (Chromat-opsia.) 
 
 When applied to a word means "The eye". 
 (Megal-ops.) 
 
 Straight, normal. (Orthoporia) normal 
 fixation. 
 
 Eye. 
 
 A growth or new growth. (Trach-oma.) 
 
 Light. (Photo-phobia.) 
 
 Lens. (Crystalline lens.) (A-phakia.) 
 
 Stroke. (Paralysis.) (Cyclo-plegia.) 
 
 Falling. (Blephar-ptosis.) (Phacia-ptosis.) 
 
 Pear. (Photo-phobia.) 
 
 A point. (Punctum Proximum.) 
 
 False. (Pseudo Myopia.) 
 
 Tendency to swerve. (Hyi)er-phoria.) 
 
 A prefix denoting "Pus". (Pyo-rrhea.) 
 
 A prefix denoting "Many". (Poly-coria.) 
 
 Pertaining toi the eyelids. 
 
 Old. (Presby-o-pia.) 
 
 A flow or discharge. (Dacry-o-rrhea.) 
 A network of sensitive layers. 
 
 An appearance. (Solo-spectrum.) 
 Contraction, cram]). (Clonic spasm.) 
 Pertaining to old age. (Arcus senilis.) 
 Strong, or strength. (A-sthen-opia.) 
 
Ketchum's Lessons ox the Eve 
 
 89 
 
 Words 
 
 Stigma 
 Sclera 
 Super 
 
 Staphy 
 
 Scope 
 
 SynechiE 
 
 Sinister 
 
 Sis 
 
 Toxin 
 Tomy 
 Tome 
 Tropia 
 Tonic 
 
 Umbra 
 Ula 
 
 Vergence 
 
 From Meaning 
 
 Greek A point. (A-stig-ma-tism.) 
 
 Greek Hard. (Scler-o-sis.) 
 
 Latin Prefix meaning "Above" or implying excess. 
 
 (Superior.) 
 
 Greek A grape. (Staphyl-oma.) 
 
 Greek Observation, to view, viewing. (Telescope.) 
 
 Greek Adhesion. (Blepharo-Synechia.) 
 
 Latin The left. (Oculus Sinister.) 
 
 Greek An Affix. Action. 
 
 Greek Poison. (Toxic Ambly-opia.) 
 
 Greek Cutting. (Irdd-ec-tomy.) 
 
 Greek A cutting instrument. 
 
 Greek Turning. (E.xo-tropia.) 
 
 Greek Continued. (Tonic Spasm.) 
 
 Latin Shadow. (Umbra-scope.) 
 
 Latin Small. (Lentic-ula.) 
 
 Latin Inclination. (Convergence.) 
 
 '^f tae Ai^^merta 
 ^ ' Opt.- metrists 
 
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