Objective: To determine whether the presence of occult choroidal neovascularization (CNV) influenced the anatomic and visual acuity outcomes in a randomized clinical trial of krypton red laser photocoagulation to treat juxtafoveal neovascular lesions in age-related macular degeneration.
Design, setting, and patients: The fluorescein angiograms obtained at the baseline examination at tertiary retinal referral centers between April 1, 1981, and December 31, 1987, as part of the Macular Photocoagulation Study (MPS) Age-Related Macular Degeneration Study-Krypton Laser were evaluated retrospectively at the MPS Fundus Photograph Reading Center by two senior readers independently (with open adjudication of any differences) from 1992 to 1994. Criteria for classifying classic and occult CNV by the MPS Group were established in 1989, 2 years after the last patient had been assigned randomly to treatment or observation in the krypton laser study.
Main outcome measures: Treatment coverage of classic and occult CNV, persistent CNV, recurrent CNV, and visual acuity from scheduled follow-up examinations for up to 5 years were analyzed for the absence or presence of occult CNV at baseline.
Results: The number of eyes with classic CNV but not occult CNV, classic and occult CNV, and occult CNV but no classic CNV were almost identical for the eyes assigned randomly to treatment or observation. Classic CNV almost always was covered completely with intense laser treatment; nevertheless, recurrent CNV developed in more than half of these eyes within 1 year after initial laser treatment. In contrast, in more than half of the eyes with occult CNV, more than 50% of the occult CNV was not covered with heavy laser treatment. Laser treatment was clearly beneficial for eyes with classic CNV but no occult CNV and almost equivalent to no treatment for eyes with classic and occult CNV. The few eyes with occult CNV but no classic CNV precluded conclusions about the value of treatment in this subgroup.
Conclusions: These results strengthen previous reports that laser treatment is beneficial for eyes with juxtafoveal choroidal neovascular lesions when classic CNV is present, even though CNV often recurs. Treatment of classic CNV alone in eyes with classic and occult CNV was not beneficial in this study. Distinguishing classic CNV from occult CNV can aid in the selection of patients who will benefit most from laser treatment.