Objectives: To document the incidence of choroidal neovascularization (CNV) in unaffected fellow eyes among individuals with ocular histoplasmosis and extrafoveal or juxtafoveal CNV in 1 eye; to determine whether the location and type of "histo spots" in the macula predict the site of future CNV development in second eyes; to describe changes over time in neovascular lesions present in fellow eyes at baseline; and to describe changes in visual acuity of fellow eyes with and without CNV at baseline.
Design, patients, and setting: Five-year prospective follow-up study of fellow eyes of 516 patients enrolled in 2 randomized clinical trials of laser photocoagulation of extrafoveal and juxtafoveal CNV. Best-corrected visual acuity and reading vision were measured, and both maculas were photographed at baseline and at 6-month intervals.
Main outcome measures: Cumulative incidence of CNV in fellow eyes free of neovascular maculopathy at the time of study enrollment, 5-year change in visual acuity of fellow eyes from baseline, and incidence of legal blindness (visual acuity < or = 20/200 in the better eye).
Results: Photographically documented CNV developed in 35 (9%) of 394 eyes initially free of neovascular maculopathy; nevertheless, good visual acuity was maintained in most newly affected eyes until the end of the 5-year follow-up period. Histo spots of any type in the macula at baseline tripled the risk for later development of CNV in comparison to eyes without histo spots in the macula. Although the type of histo spots present in the central macula at baseline did not predict future CNV development, in 32 of 35 second eyes in which CNV developed and in 7 of 9 fellow eyes in which a second area of CNV developed during follow-up, CNV was preceded by an "atypical" histo spot in the same location. Among 122 patients who had bilateral neovascular maculopathy initially, 100 were examined 5 years later; 8 (8%) were legally blind, compared with 3 (1%) of 339 patients examined who had unilateral CNV initially. At the 5-year examination, 355 (81%) of 439 patients examined had a visual acuity of 20/20 or better in at least 1 eye, including 74 (55%) of 134 patients who had bilateral neovascular maculopathy.
Conclusions: Although the incidence of CNV in fellow eyes that initially were unaffected remained low throughout 5 years of follow-up, it persisted at a nearly constant rate. The risk of legal blindness was low, even for patients who had bilateral involvement. Perhaps most important, 81% of all patients followed up for 5 years retained a visual acuity of 20/20 in at least 1 eye, and 20% retained this visual acuity in both eyes. Retrospective review of photographs suggests that the ophthalmologist should pay special attention to areas of the central macula in which new "atypical" histo spots are observed, with the goal of treating CNV that may develop in the same area at a time when the benefits of laser treatment may be greatest.