Interocular amplitude differences of the full field electroretinogram in normal subjects.

Aims: To determine the interocular amplitude response difference of the electroretinogram (ERG) in normal subjects. Methods: 79 subjects, without retinal changes of clinical significance, underwent ERG testing. They included 63 men and 16 women, with a mean age of 44 (SD 12) years and range of 18–65 years. Isolated rod, scotopic maximal, dark adapted 30 Hz flicker, photopic single flash, and light adapted 30 Hz flicker responses were recorded in both eyes following the International Society for Clinical Electrophysiology of Vision (ISCEV) standard protocol. The interocular percentage differences of the ERG b-wave amplitudes were calculated and presented as percentiles (25th, 50th, 75th, 95th), means (SD), and medians. Results: The median interocular percentage differences in the b-wave amplitudes for the above ERG stimulus responses were 10%, 8%, 10%, 11%, and 10%, respectively. The mean interocular percentage differences were 11%, 11%, 12%, 13%, and 14%. The 95th percentiles for the interocular percentage differences were 28%, 27%, 36%, 33%, and 35%, respectively. Conclusions: The interocular percentage differences in the ERG b-wave amplitudes for five different stimulus responses were similar in our cohort of individuals without clinically significant retinal changes and ranged from a median of 8–11% and a 95th percentile of 27–36%. Our findings should be useful for determining sample sizes in future therapeutic trials on retinal diseases with monocular therapeutic strategies and may also have application for the more accurate detection of asymmetric retinal disease.