Objective: To determine the effects of subthreshold 810-nm-diode laser treatment on the rate of development of choroidal neovascularization (primary end point) and the effect on visual acuity (VA) in participants with multiple large drusen in one eye and a preexisting neovascular age-related macular degeneration (AMD) lesion in the other. Design: Multicenter, prospective, randomized controlled trial. Participants: Two hundred forty-four patients ≥50 years of age and with a neovascular or advanced AMD lesion in one eye and, in the fellow "study" eye, (1) at least 5 drusen ≥ 63 μm in diameter, (2) Early Treatment Diabetic Retinopathy Study best-corrected VA (BCVA) of 20/63 or better, and (3) no evidence of neovascularization at baseline. Methods: Patients were randomized to treatment or observation of their study eye at each of 22 centers. At each visit, the protocol specified that BCVA, a complete retinal examination, and fluorescein angiography be documented. Treated eyes had a grid of 48 extrafoveal, subthreshold diode (810 nm) laser spots, 125 μm in diameter, placed in an annulus outside of the foveola. Patients were seen at baseline and at 3, 6, 12, 18, 24, 30, and 36 months after randomization. No retreatments were allowed. Main Outcome Measures: Development of choroidal neovascularization (as confirmed by fluorescein angiography) and change in BCVA. Results: Throughout follow-up, the rate of choroidal neovascularization events in treated eyes consistently exceeded that in observed eyes. At 1 year, the difference was 15.8% versus 1.4% (P = 0.05). Most of the intergroup differences in choroidal neovascularization events occurred during the first 2 years of follow-up. Treated eyes showed a higher rate of VA loss (≥3 lines) at 3- and 6-month follow-ups relative to observed eyes (8.3% vs. 1% and 11.4% vs. 4%, respectively; Ps = 0.02, 0.07). After 6 months, no significant differences were observed in VA loss between groups. Conclusion: Prophylactic subthreshold 810-nm-diode laser treatment to an eye with multiple large drusen in a patient whose fellow eye has already suffered a neovascular event places the treated eye at higher risk of developing choroidal neovascularization. We advise against using prophylactic subthreshold diode laser treatment in these eyes.
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