■ BACKGROUND AND OBJECTIVE: To determine the prophylactic and therapeutic value of a single subthreshold 810-nanometer laser treatment in patients with high risk drusen as a manifestation of dry age-related macular degeneration in both eyes. ■ PATIENTS AND METHODS: The Prophylactic Treatment of Age-related Macular Degeneration study enrolled 1,278 eyes of 639 participants who were 50 years or older with at least 5 drusen 63 μm or more in diameter in each eye. Treatment consisted of the placement of an annular grid of 48 extrafoveal, subthreshold 810-nm diode laser applications centered at but sparing the foveola in one eye of each participant, with the fellow eye serving as a control. Development of choroidal neovascularization and change in best-corrected visual acuity were compared between treated and untreated eyes. ■ RESULTS: Subthreshold laser treatment did not decrease the incidence of choroidal neovascularization in treated versus untreated eyes. A modest visual acuity benefit in treated eyes was found at 24 months (1.5 letter difference; P = .04) and in the treated eyes of participants with a baseline visual acuity between 20/32 and 20/63 (4.0 letter difference; P = .0034). However, this treatment effect was not sustained at 3 years. ■ CONCLUSION: A single subthreshold 810-nanometer laser treatment to eyes of participants with bilateral high risk drusen is not an effective prophylactic strategy against choroidal neovascularization.
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