Early peripheral laser photocoagulation of nonperfused retina improves vision in patients with central retinal vein occlusion. Results of a proof of concept study.

Abstract

Dear Editor, We read with interest the article by Rehak et al. [1] describing improvements in vision among patients with retinal vein occlusion (RVO) following laser photocoagulation to areas of peripheral retinal nonperfusion. Their findings add to the growing body of evidence in the literature of the relevance of assessing peripheral manifestations of retinal disease, which has been greatly enhanced by the advent of ultra-widefield imaging devices [2–8]. In particular, it is increasingly evident that peripheral retinal nonperfusion plays an important role in regulating vascular endothelial growth factor (VEGF) production in patients with retinal vascular diseases, with consequent effects on retinal neovascularization and macular edema [6–8]. In this study, the authors calculated the ratios of the total extent of nonperfused areas in relation to the optic disc area, and included patients with ratios from 1 to 10 [1]. This represents a relatively small area of nonperfusion compared to the total surface area of the retina. Earlier studies assessing areas of nonperfusion using widefield fluorescein angiography used the ischemic index, which is the ratio of the area of nonperfused retina as a percentage of the total visible retina [7]. In a paper by Tsui et al. [7] the mean ischemic index was 25 %, and ranged from 0 % to 100 %. Singer et al. [8] reported a mean ischemic index of 14.8 %, with a range of 0 % to 67.7 %. In addition, patients with ischemic index >10 % had significantly greater mean central subfield thickness on presentation compared to those with ischemic index ≤10 % (520.8 μm vs 424.5 μm) [8]. It is possible that among patients with larger areas of peripheral nonperfusion, laser photocoagulation may have had a greater impact on the control of macular edema and improvement in visual acuity compared to patients with relatively smaller areas of peripheral nonperfusion. We agree with the authors’ comment that “further research evaluating the changes of the retinal perfusion in patients with RVO under different treatments (anti-VEGF, steroids, or photocoagulation) is required” [1]. In their study, both the experimental group and group treated with ranibizumab injections demonstrated increases in the area of nonperfusion over the 6-month period. Other studies, however, have demonstrated decreases in the areas of nonperfusion following treatment. Singer et al. [8] reported a significant decrease in the mean ischemic index when edema was present compared to when edema had resolved (14.8 % vs 10.3 %). In addition, in a paper by Campochiaro et al. [9], reperfusion of nonperfused retina was observed in between 6 % to 8 % of patients with RVO treated with intravitreal ranibizumab, compared to 1 % of sham-treated patients. Also, at 6 months, the proportion of patients with no evidence of retinal nonperfusion was higher among groups treated with ranibizumab when compared to the sham group (82.0 % C. S. H. Tan : L. W. Lim Department of Ophthalmology, Tan Tock Seng Hospital, Singapore, Singapore