Laser treatment in fellow eyes with large drusen: updated findings from a pilot randomized clinical trial

Abstract

Purpose To update the findings from the Choroidal Neovascularization Prevention Trial (CNVPT) with respect to resolution of drusen, incidence of choroidal neovascularization, and visual function. Design A multicenter, randomized, controlled, pilot clinical trial. Participants The 120 patients enrolled in the CNVPT. Patients had signs of choroidal neovascularization or retinal pigment epithelial detachment in 1 eye and had ≥10 large (>63-μm) drusen in the contralateral, or fellow, eye. Intervention The fellow eye of 59 patients was assigned randomly to argon green laser treatment consisting of multiple 100-μm spots at least 750 μm from the center of the fovea. The fellow eye of the remaining 61 patients was assigned randomly to observation. Main outcome measures Change in visual acuity was the primary outcome measure. Incidence of choroidal neovascularization, resolution of drusen, change in contrast threshold, change in critical print size for reading, and incidence of geographic atrophy were secondary outcome measures. Results Throughout 4 years of follow-up, there were no statistically significant differences in change in visual acuity, contrast threshold, critical print size, or incidence of geographic atrophy. With additional follow-up, the large increase in the incidence of choroidal neovascularization observed within 18 months of treatment was maintained; however, by 30 months, the incidence in the two treatment groups was the same. Most drusen resolution in treated eyes occurred within 24 months of the initial treatment. Treated eyes that received higher-intensity laser burns had an increased risk of choroidal neovascularization. Among eyes developing choroidal neovascularization in each treatment group, most lesions (two thirds or more) were composed of occult neovascularization only. Conclusions Laser treatment as applied in the CNVPT caused an excess risk of choroidal neovascularization in the first year or so after treatment. The increased early incidence of choroidal neovascularization was not associated with either a harmful or beneficial effect in this pilot study.