key: cord-0778393-cng2e1r4
authors: Thibault, Mace; Valentin, Pipelart
title: Acute macular neuroretinopathy and SARS-CoV-2 infection : case report
date: 2021-09-09
journal: J Fr Ophtalmol
DOI: 10.1016/j.jfo.2021.07.004
sha: 8db41ed0a3d54b18f1a8d0b95105ea7bc0cff007
doc_id: 778393
cord_uid: cng2e1r4

Purpose: To compare anterior segment parameters evaluated with optical low coherence reflectometry and combined Scheimpflug-Placido disc topography in eyes with different axial lengths. Methods: 204 patients were divided into 3 groups according to their axial lengths. Central corneal thickness (CCT), anterior chamber depth (AD), mean keratometry value (K mean) and white-to-white distances (WTW) obtained from both devices were compared. All measurements were performed 3 times and averaged. Results: In group 1, a significant difference was detected between the two devices for CCT, WTW and Kmean measurements (p<0.001, p<0.001, p:0.005 respectively). In group 2, a significant difference was detected between the two devices for WTW measurement (p<0.001). In group 3, a significant difference was detected between the two devices for CCT and WTW measurement (p<0.001, p<0.001 respectively). In the Bland-Altman analysis, there was no match for Kmean obtained with both devices in group 1. In group 2, there was no agreement for AD obtained with both devices. In group 3, there was no match for AD, WTW or Kmean values obtained with both devices. Conclusion: Some anterior segment parameters are not suitable for interchangeability in eyes with different axial lengths evaluated by Lenstar and Sirius anterior segment imaging systems. When planning critical surgery and treatment, more attention should be paid to measurements in eyes of different axial lengths.

It is important to accurately and precisely measure the parameters of the anterior segment in the diagnosis, follow-up, and treatment of diseases related to the anterior Page 5 of 21 J o u r n a l P r e -p r o o f segment, such as glaucoma and corneal diseases. Today, different devices such as Scheimpflug corneal topographic imaging, optical coherence tomography (OCT), interferometry, ultrasonic biomicroscopy, and scanner-slit topography are widely used to evaluate the anterior segment. [1] All these devices should be used interchangeably to measure anterior segmet parameters, and the measurements made should be compatible in themselves. Thus, surprises are not encountered in clinical and surgical results.

Keratometry is an anterior segment parameter that we use in monitoring the diagnosis, follow-up and treatment results of corneal diseases such as keratoconus, calculating intraocular lenses and prescribing contact lenses. [2] [3] [4] We use white-to-white (WTW) distance measurement when prescribing contact lenses or when refractive surgery is planned. It is also a parameter that we apply for phakic IOLs, which is one of the refractive surgical methods. In the 4th generation iol formulas used in recent years, WTW distance measurement is also used. [5] [6] [7] Measurement of aqueous depth (AD) and central corneal thickness (CCT) is used to determine the risk of angle closure in a wide range of ways, from the diagnosis of glaucoma to refractive surgery [8, 9, 10] Sirius corneal topography (CSO, Florence, Italy) is a new device using the Scheimpflug camera and Placido disc technologies, which is a combined system. Corneal thickness, AD, anterior chamber depth, lens thickness, limbus-limbus distance, keratometry, and anterior and posterior corneal topography measurements can be made with Sirius. Lenstar LS 900 (Haag-Streit AG, Köeniz, Switzerland) is a device that works with the principle of optical low coherence reflectometry, which offers various dimensions of the eye with a single measurement. Axial length, WTW, CCT, Aqueous depth (distance between corneal endothelium and lens anterior capsule), anterior chamber depth (distance between corneal epithelial lens anterior capsule), crystal lens thickness and keratometric values can be measured with Lenstar. In previous studies, similar devices using both methods have been shown to give repeatable and reliable measurements. [11] [12] [13] However, in all of the studies, axial lengths were done without grouping. There are a limited number of studies in the literature on the repeatability and reliability of measurement of the front segment parameters of both devices with different axial lengths. This study is one of the first studies to evaluate the anterior segment parameters measured in healthy eyes classified according to different axial lengths with Lenstar and Sirius devices.

In this prospective study, we included patients who presented to our clinic with various complaints. Those with systemic or ocular pathology that may affect eye measurements, those with a history of eye surgery, and those with high refraction (± 6.00 spherical and ± 3.00 cylinder) were not included in the study. Before the study, we received informed consent from all patients and conducted the entire study by the Helsinki declaration. We classified the patients into 3 groups according to their axial length. We have classified the axial length below 22.0 mm into the 1st group, between 22-24.50 mm into 2nd group and above 24.50 mm to 3rd group. All measurements were made by selecting the order of the devices randomly by the same person and taking 3 measurements from each device. The pupil was not dilated for the measurement. CCT, AD, WTW, anterior Keratometry (mean) values were measured from all participants. All measurements were made automatically by the device.

Lenstar biometry has the principle of optical low coherence reflectometry, a technology similar to OCT. The device uses an 820 nm superluminescent diode laser to measure intraocular measurements and pachymetry. The 950 nm light-emitting diode (LED) is used for keratometry, limbus-limbus distance measurement, and pupillometry. (table 1) There was a significant difference between the two devices for WTW measurement in group 2 (p <0.001). (table 2) In group 3, a significant difference was detected between the two devices for CCT, WTW measurements. (p <0.001, p <0.001 respectively) (table 3) All values in the three groups were correlated in both devices. The agreement of the measurements of both devices with each other was evaluated with Bland-Altman graphics.

Accordingly, the lower and upper limits of the 95% agreement limit were determined. In Bland-Altman analysis, the CCT, AD and WTW values obtained with both devices in the 1st group were narrower than 95%, and there was good agreement between the devices. 

In this study, we evaluated the repeatability of the anterior segment parameters obtained with Sirius and Lenstar LS900 biometry, which is a topography system using We determined CCT, WTW and Kmean measurements in those whose axial length is between 22mm-24.5 mm can be used instead of each other in each device. We found the AD value can not be used interchangeably. In those with axial length over 24.5 mm, we determined CCT measurements to be usable in each device instead of each other. The name, WTW, and Kmean values are not used in place of each other.

In cataract surgery, which is the most frequently applied in an ophthalmology practice, accurate calculation of intraocular lens (IOL) power is important for post-surgical patient satisfaction. Inaccuracy in axial length, keratometry and AD measurement, one of the anterior segment parameters, result in incorrect IOL power calculation. [14] At the same time, AD provides important clinical information in determining the risk of angleclosure in narrow-angle glaucoma and phakic IOL surgery. [15] The curvature of the cornea, another anterior segment parameter, is a parameter used in determining the amount of astigmatism, the direction of the astigmatism axis, the power calculation of the IOL to be implanted, and many critical stages of refractive surgery planning. [16, 17] Measuring the distance from white to white (WTW) is important in preoperative evaluation in refractive and cataract surgery. WTW measurement should be done precisely to encounter long-term stabilization and less complication of İOL in the anterior chamber in the anterior or phakic iodine. [18, 19] Therefore, to compare the accuracy of the data obtained from the anterior segment analyzers in eyes with different Page 10 of 21 J o u r n a l P r e -p r o o f characteristics, it is necessary to compare with the reference devices, which are accepted as the gold standard in the measurement of these parameters.

Nowadays practice, Optical coherence tomography and ocular ultrasonography (US) are the most widely used and accepted gold standard for measuring intraocular distance ACD / AD and CCT. However, since US is a contact method, it is a method that requires the use of topical anesthesia, leading to the risk of corneal infection and patient discomfort. [20, 21] US is a method dependent on user experience and good patient compliance. These disadvantages have led to the use of non-contact, noninvasive devices.

Ocular corneal topography systems that are available today have been rapidly developed due to increased interest in corneal refractive surgery and refractive phakic intraocular lens (IOL) implantation techniques.

In a study by Chen et al, Lenstar and Sirius devices in terms of CCT and WTW compliance and repeatability were examined and CCT in terms of Sirius in favor of lenstar in terms of WTW in favor of high measurements were found. [22] In a similar study conducted by Bayhan et al, CCT was also found to be a high measurement in favor of lenstar, while there was no difference between WTW and K flat/steep. [23] Although the data obtained in both studies were statistically significant, they were not clinically significant and were found to be interchangeably usable in both devices. In another study by Huang et al, there is a high measurement in favor of corneal topography in CCT and AD measurements while a high measurement in favor of corneal topography was taken in favor of Kmean value biometry. According to Bland-Altman analysis, both devices were found to be interchangeable. [24] However, all the studies were done without grouping axial lengths. In these devices, which work according to optical principles, measurements of an average axial length may not be expected to deviate much, but measurements of Both Sirius and the Lenstar device use image analysis to obtain keratometry values and convert the measured radius to diopter using the standard 1.3375 refractive indexes. In previous studies, it has been reported that it gives measurements compatible with Sirius and Lenstar in terms of keratometry measurements. [23] In our study, the keratometry values obtained from Lenstar and Sirius devices were similar, but in eyes with axial length below 22mm and above 24.5mm, they did not have a narrow 95% agreementlimit in some anterior segment parameters to show good agreementbetween the devices.

In his study, Chen W et al found that it gives lenstar and Sirius compatible measurements in terms of WTW measurements and can be used interchangeably. [22] In our study, the eyes with an axial length of over 24.5 mm did not have a narrow fit in 95% In our study, there was a correlation in all groups in terms of CCT, and we found that two devices could be used interchangeably according to the results of Bland Altman analysis comparing the agreementof the two measurement techniques.

There were some limitations with our study that refractive disorders in eyes with different axial lengths could affect the measurements. For this reason, we did not include those with high refractive disorders (those with spherical equivalent over +/-6 D and those with +/-5 D cylindrical equivalent). Another limiting factor was the relatively low number of patients. In future studies, we find it appropriate to carry out similar studies on larger series that will be included in patients with high refractive disorders.

The repeatability and agreementof measurement devices, which are used frequently in the diagnosis, follow-up, and treatment of anterior segmentation diseases, is extremely important. The consistency of the measurements strongly affects the treatment success of the patients. In our study, we evaluated the eyes of different axial lengths by applying a method that was not done in previous studies. In these eyes, we got results that are partially compatible with other studies. However, we concluded that in some anterior segment parameter values, the two devices cannot be used interchangeably in eyes with different axial lengths. This made us think that we should be more careful in measurements in different axial lengths of eyes when planning critical surgery and treatment.

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