Purpose: We explored the clinical impression that geographic atrophy of the retinal pigment epithelium, a form of advanced age-related macular degeneration, is perceived by the patient as progressing gradually, even when fixation switches from foveal to extrafoveal.
Methods: We analyzed the responses of 60 patients with geographic atrophy to a questionnaire administered as part of a five-year study of the natural course of geographic atrophy, funded by the National Eye Institute. We performed scanning laser opthalmoscope perimetry on all patients. We examined two additional patients with geographic atrophy who reported abrupt visual loss.
Results: No eye with geographic atrophy was reported by any patient to have had sudden visual loss. Although most patients with geographic atrophy show foveal fixation until the fovea is atrophic and then show extrafoveal fixation, scanning laser ophthalmoscope perimetry in three patients with geographic atrophy showed alternation between a foveal and an extrafoveal retinal locus for fixation. Two patients with geographic atrophy who complained of abrupt visual loss were found to have occult choroidal neovascularization, which evolved in one patient to classic choroidal neovascularization. The neovascularization was difficult to detect because of the presence of geographic atrophy and its associated ophthalmoscopic and fluorescein angiographic features.
Conclusions: Visual loss in geographic atrophy is nearly always perceived by the patient as being gradual, even when considerable decreases in visual acuity occur and when foveal vision and fixation are lost. A possible explanation for this perception is that there is a transitional period during which a patient uses both a foveal and extrafoveal site for fixation. The complaint of abrupt visual loss in a patient with geographic atrophy should raise the suspicion of choroidal neovascularization, which may be occult and difficult to detect.