The effect of refractive error on pattern electroretinograms in primates.

The effect of optical blur on the steady-state (6, 8, 10 Hz) counterphase pattern electroretinogram (PERG) was measured in three normal cynomolgus monkeys. Blur was induced using lenses of -8.00 to +12.00 diopters, and monocular PERGs were recorded at a viewing distance of 0.32 meters. A substantial decrease in PERG amplitude occurred with a 0.51 cpd grating when +4.00 diopters of blur or greater were used. PERG amplitude to a 1.25 cpd grating decreased with lenses greater than +2.00 diopters. Minus lenses caused a steep decline in PERG amplitude of both spatial frequency gratings. These results indicate that refractive state has a significant effect upon the PERG and should be carefully considered in electrophysiologic testing of the primate visual system.