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T.R. Friberg, PTAMD Study Group; The Prophylactic Treatment of AMD Multi–Centered Trial (PTAMD): Results From the Bilateral Study Arm . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3538.
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To determine in a prospective randomized trial whether a grid of prophylactic subthreshold laser placed in an eye with drusen has a prophylactic benefit (protecting it from choroidal neovascularization) or a therapeutic benefit (improvement of visual acuity) compared to the untreated fellow eye.
639 participants with at least 20/63 visual acuity in both eyes and at least 5 large drusen (63 microns or greater) in each eye were randomized as to which eye was to receive subthreshold laser treatment (810 nm laser, 125 micron spot size, 48 lesion) in a one–time application. 22 centers participated in the study. Participants were followed by fundus photography, fluorescein angiography, and best corrected ETDRS visual acuity for up to 5 years. As eyes with good visual acuity at baseline might not be expected to improve, participants with 20/32 to 20/63 vision were evaluated as a separate subgroup in a planned analysis. The Data Safety Monitoring Committee (DSMC) monitored the study continually.
There was no difference in choroidal neovascularization event rates between treated and untreated eyes at 3 years. Substantial drusen reduction (50% or more) occurred following treatment in 44.5% of treated eyes versus 4.5% of observed eyes at 12 mo and 47.1% versus 9.0% at 24 mo (P < 0.001 for each). In all study patients taken in aggregate, visual acuity at 24 mo showed a 1.5 letter beneficial difference compared to observed eyes (P = 0.04) and treated eyes showed a higher percentage of 2 lines of visual acuity gain (12 vs 8%). In the subgroup of eyes with baseline vision from 20/32 to 20/63, treated eyes showed a 4.0 letter (1 line = 5 letters) benefit over observed eyes at 24 months. Treated eyes also showed a higher percentage of eyes with 2 or more lines of visual acuity gain (31% vs 19%, P=0.025) and less visual acuity loss (13% vs 22% losing 2 or more lines, P=0.04).
Subthreshold laser treatment to eyes with drusen per the PTAMD protocol was not protective against subsequent choroidal neovascularization. However, a modest treatment benefit was found, particularly in eyes where the pretreatment visual acuity was between 20/32 and 20/63.
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