Foveal cone ERGs in fellow eyes of patients with unilateral neovascular age-related macular degeneration.

Objective: To determine whether fellow eyes with normal visual acuity of patients with unilateral neovascular age-related macular degeneration (AMD) have retinal malfunction.

Methods: Foveal cone electroretinograms (ERGs) were recorded from fellow eyes with visual acuities of 20/25 or better of 73 patients with unilateral neovascular AMD and from 28 normal volunteers of comparable age. Responses were elicited with a 4 degrees stimulus flickering at 42 Hz presented by a stimulator-ophthalmoscope.

Results: The study eyes of the patients were found to have foveal cone ERGs that, on average, were normal in amplitude but delayed in implicit (peak) time after adjustment of the data for age, sex, iris pigmentation, and refractive error by multiple linear regression. Based on all subjects, amplitude declined with increasing age and was smaller in eyes with darker irides; implicit time increased with increasing age.

Conclusions: These findings suggest that fellow eyes with normal visual acuity of patients with unilateral neovascular AMD tend to have foveal cones that are normal in number but that function abnormally. In addition, foveal cone ERG amplitude should be adjusted for both age and iris pigmentation and implicit time should be adjusted for age when assessing retinal function of elderly patients.