Choroidal Thickness in Nonarteritic Anterior İschemic Optic Neuropathy

We read with interest the article entitled “Choroidal Thickness in Nonarteritic Anterior Ischemic Optic Neuropathy,” by Schuster and associates. The authors have investigated the choroidal thicknesses (CT) in patients who had nonarteritic anterior ischemic optic neuropathy (NAION) at the acute stage and reported that the affected eyes of patients who had acute NAION and their contralateral, unaffected eyes showed significantly thinner macular CTs than the eyes of healthy subjects. Therefore, the authors have proposed that a thin choroid might be a diagnostic feature of NAION. We thank the authors for their intriguing study and would like to make some contributions with respect to 2 points for further CT studies in NAION.

First, for the choroidal thickness measurements, they used 1 horizontal section passing through the center of the fovea, which was evaluated on this section at 7 points, and separately compared these measurements between the patient and the control groups. However, taking optical coherence tomography (OCT) measurements at 1 selected point and comparing these to each other is not the most precise method for determining CTs, since these measurements, which are performed manually, could be affected by local irregularities of the choroid-scleral boundary. Therefore, several points in the same horizontal sections of the macula could be measured to reduce the risk of mistakes. The average of these measurements could then be compared. However, in future, the development of automatic software for CT measurements will help to improve the accuracy of these measurements.

In addition, CT measurements could be affected by a number of factors such as age, sex, spherical equivalent, axial length, diurnal variation, smoking, coffee addiction, and some conditions such as diabetes mellitus and age-related macular degeneration. To eliminate these potentially confusing factors, the authors have statistically adjusted some of them for comparisons; however, these adjustments did not include all the factors mentioned above. Also, in their study, although there was a significant difference in terms of the CTs between the acute NAION patients and the healthy subjects, there were no significant differences between the CT measurements of the affected and unaffected eyes in patients with acute NAION and between their affected and previously affected eyes. This might support the assertion that the study by Schuster and associates could have been influenced by these confusing factors. In contrast to this study, Dias-Santos and associates have reported that the mean CT is significantly higher in patients with chronic NAION than in healthy subjects and that this might be a marker of the local dysfunction of the vascular autoregulation mechanisms of the choroid. These authors also reported that there is a statistical association between CT and the amount of time after the ischemic attack. However, Schuster and associates have reported that, in terms of the CTs, the affected eyes of patients who had acute NAION did not differ significantly from their contralateral eyes that had previously been affected by NAION. Because of these conflicting case-control studies, further prospective studies with larger sample sizes as well as follow-up studies are needed to validate these results.

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Jan 7, 2017 | Posted by in OPHTHALMOLOGY | Comments Off on Choroidal Thickness in Nonarteritic Anterior İschemic Optic Neuropathy

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