Predictors of drusen reduction after subthreshold infrared (810 nm) diode laser macular grid photocoagulation for nonexudative age-related macular degeneration

PURPOSE: To determine the predictors of drusen reduction in eyes with nonexudative age-related macular degeneration (ARMD) treated with subthreshold infrared (810 nm) diode laser macular grid photocoagulation. Additionally, to determine the relationship of laser-induced drusen reduction and best-corrected visual acuity (BCVA) 18 months after laser treatment.DESIGN: Randomized controlled clinical trial.METHODS: Fifty patients (100 eyes) with bilateral nonexudative ARMD were enrolled at two centers. One eye of each patient was randomized to the observation; the other eye was treated with 48 subthreshold (invisible end point) applications of infrared (810 nm) diode laser in a macular grid pattern. The eyes that received subthreshold laser treatment were compared with the eyes that received no treatment. The baseline fundus characteristics (number, size, and distribution of drusen, as well as focal hyperpigmentation) from two macula areas (central 1500 micro diameter, pericentral 1500 micro ring area) on stereo color photographs, the number of laser-induced lesions, and the area of laser induced retinal pigment epithelial (RPE) lesions on fluorescein angiography 3 months after treatment were studied as predictors of major drusen reduction (> or = 50% drusen reduction from baseline) 18 months after laser treatment. BCVA at baseline and 18 months later was compared in observation eyes and in laser-treated eyes.RESULTS: Eighteen months after randomization, 24 (48%) of 50 eyes treated with subthreshold laser had major drusen reduction compared with three (6%) of 50 observation eyes (P =.00001). At 3 months post-treatment in laser-treated eyes with major drusen reduction, the mean number of laser-induced lesions on fluorescein angiography was 30.7 and the mean area of RPE change was 0.81 mm(2) compared with 14.8 laser-induced lesions and 0.35 mm(2) area of RPE change in eyes without major drusen reduction (P =.0001 and P =.0003, respectively). At baseline, fundus characteristics were not significantly different between observation eyes and laser-treated eyes or between the major drusen reduction group and the nonmajor drusen reduction group. At 18 months after treatment, BCVA was not significantly different in laser-treated eyes and in observation eyes.CONCLUSIONS: Subthreshold infrared (810 nm) diode laser macular grid photocoagulation in eyes with nonexudative ARMD significantly reduced drusen 18 months after laser treatment. Both the number of subthreshold laser lesions and the area of RPE changes visible on fluorescein angiography 3 months after treatment appeared to be predictors for major drusen reduction 18 months after treatment. However, it remains to be determined whether laser-induced drusen reduction is beneficial for visual acuity or reduces the incidence of choroidal neovascularization (CNV) in eyes with nonexudative ARMD.