The Scotopic and Photopic Bar-Pattern ERG — Contributions of the Central and Peripheral Retina

Abstract

The alternating phase bar-pattern ERG is used to investigate the contribution of specific retinal areas and specific retinal components to the ERG. Photopic and scotopic bar-pattern ERG’s are recorded under proper lighting conditions. The photopic ERG response is found to be proportional to the number of cones in the retinal area stimulated out to 18° from fixation and not to the total number of receptors.

Most previous studies using the bar-pattern ERG response from discrete areas of the retina have centered on the photopic response (Johnson, et al., 1966). In addition, Armington (1968) showed that under appropriate conditions a scotopic response could be elicited. We wished to determine if the activity of a given receptor population could be associated with a response produced under a given set of stimulus area and luminance conditions. We have compared the scotopic and photopic b-wave responses to the number of cones and rods in different areas of the retina to determine the relative contributions of these elements. The alternating phase bar-pattern stimulus was used because it eliminates the problem of scattered light and allows the stimulation of a specific area of retina without stimulating the rest of the retina.

Supported in part by NIH NEI Grant No. EY 00412.