Focal proliferations of retinal pigment epithelium. Risk factor in senile macular degeneration

BACKGROUND: Clinical studies have demonstrated the relevance of focal RPE proliferations in early AMD as risk factors for visual loss caused by late AMD. Angiographically these focal RPE proliferations are characterized as small hypofluorescent spots with hyperfluorescent rim without leakage. Corresponding to histological and experimental studies they can be interpreted as small areas of occult choroidal neovascularizations covered by proliferated RPE cells. The characterization of the long-term prognosis of these lesions was the aim of the present study. PATIENTS AND METHODS: Ninety-eight patients (52 female, 46 male) were reexamined clinically and angiographically with a follow-up of 2-12 years (mean 6.5 years). RESULTS: Visual loss of two lines or more could be observed in 64.5% of patients with final visual acuity less than 20/100 in 24.5% of patients. Morphologically the changes in visual acuity were related to the progression towards classical choroidal neovascularizations in 32.7% of patients. In addition 11.2% of patients demonstrated a regression of the small occult membrane with the development of small areas of RPE atrophy covering the size of the original occult neovascularization. In 10.2% of the patients enlargement of the lesion was observed, resulting in a large occult choroidal neovascularization without signs of classical membranes, and in 45.9% of patients the clinical and angiographical situation was unchanged. The most important prognostic factor correlating with visual loss was the presence of a disciform lesion in the fellow eye and of multiple drusen in the examined eye. Other factors like the size or location of the focal RPE proliferation and the duration of follow-up did not correspond with visual loss. CONCLUSIONS: Focal RPE proliferations in early AMD interpreted as small occult choroidal neovascularizations are associated with a high risk of visual loss. Especially if these lesions are associated with multiple drusen and a disciform lesion in the fellow eye, nearly all patients are at risk for visual loss. These changes may therefore characterize a special high-risk group for future prophylactic treatments in early AMD, but because of the high risk for the development of classical choroidal neovascularizations in this group, these results are also very important for the planning of prophylactic laser trials for drusen in early AMD.