Objective: This study aimed to describe the short-term effects of low-intensity laser treatment in eyes with drusen at risk of having choroidal neovascularization (CNV) develop secondary to age-related macular degeneration.
Design: The study design was a multicentered, randomized clinical trial of laser treatment versus observation.
Participants: One hundred fifty-six patients without exudative age-related macular degeneration and with more than 10 large (> 63 microns) drusen in each eye were enrolled in the Bilateral Drusen Study. One hundred twenty patients with exudative age-related macular degeneration in 1 eye and more than 10 large drusen in the other eye were enrolled in the Fellow Eye Study.
Intervention: The treatment protocol for most (85%) of the eyes consisted of 20 laser burns, 100 microns in diameter, in a pattern of 3 rows placed between the 12- and 6-o'clock positions beyond the temporal perimeter of the foveal avascular zone. The desired intensity of the burns was a gray-white lesion. Whenever the area of drusen had not been reduced by 50% or more at 6 months, a second treatment was applied nasal to the fovea in a mirror image of the first treatment. During the last 6 months of enrollment, a second laser treatment protocol was adopted that specified 24 laser burns, 100 microns in diameter, in a circular pattern of 2 rows surrounding the macular drusen.
Main outcome measures: Change in visual acuity is the primary outcome measure. Incidence of CNV, change in contrast threshold, and change in critical print size are secondary outcome measures.
Results: In the Bilateral Drusen Study, CNV developed in 4 of 156 treated eyes and in 2 of 156 observed eyes (P = 0.62); in the Fellow Eye Study, the proportions are 10/59 treated eyes and 2/61 observed eyes (P = 0.02). Changes in visual acuity are similar in treated and observed eyes in the Bilateral Drusen Study through 18 months. However, by 18 months, observed eyes in the Fellow Eye Study have lost more visual acuity than treated eyes (P = 0.02). Changes in contrast threshold are similar in treated and observed eyes in each study.
Conclusions: Laser treatment to high-risk fellow eyes may increase the short-term incidence of CNV. Long-term effects in fellow eyes and effects in patients with bilateral drusen require additional observation.