Normative data and control studies of flash VEP's for comparison to a clinical population

The effects of aging, interocular comparisons, pupil dilation, iris pigmentation, and simulated cataracts on bright flash visual evoked potentials (VEP's) of normal observers were studied to assess the flash VEP as a potential predictor of postsurgical visual function in cataract patients. Seventy-six observers (from 20 to 80 years old) were tested for age differences in flash VEP's. Implicit time measures for transient responses increased significantly as a function of age, but neither transient nor steady-state response amplitudes were altered significantly. Moreover, no significant changes in VEP's occurred as a function of interocular comparisons, pupil dilation, or differences in iris pigmentation of normal observers. Simulation of cataracts with 14 observers did not affect implicit time measures, but did change response amplitudes significantly. Therefore, implicit time measures of cataract patients should be compared either to those of normal age-matched controls or, in the case of a unilateral problem, to the normal fellow eye. Delayed implicit time measures, after the appropriate comparison, suggest optic nerve/pathway dysfunction. However, comparisons of amplitude measures require compensation for opacity density.