Normal values of Focal Electroretinograms, and the Clinical Applications

ABSTRACT

Focal cone electroretinograms were performed with 5-degree white flickering stimuli on 100 normal eyes and 50 eyes with known macular diseases. Responses were obtained under direct visualization of the fundus with hand-held stimulator-ophthalmoscope (FSC-500) produced by LKC Technologies. Mean foveal cone amplitude for 100 normal eyes was 449.6 nV and mean implicit time was 34.8 msec, and ninty five percent of normal eyes had amplitudes greater than 320 nV, and implicit time less than 48.5 msec. There was a statistically significant inverse correlation between amplitude from fovea and age (r=-0.93, p< 0.05). In eyes with known maculopathy, mean foveal cone amplitude was well correlated with visual acuity. Over ninty percent (29/32) of eyes with visual acuity of 0.5 or poorer showed significant reduction in amplitude, even after correcting aging effect. We suggest that the focal electroretinogram is a sensitive and useful test for detecting macular abnormalities.