Induced refractive errors and pattern electroretinograms and pattern visual evoked potentials: implications for clinical assessments.

Refractive errors were induced in normal subjects by means of positive dioptre lenses to reduce visual acuity (VA) from an initial level of 20/20 to 20/100 and then to 20/200. Pattern electroretinograms (PERGs) and pattern visual evoked potentials (PVEPs) were simultaneously recorded at each of these 3 levels of VA using high contrast checkerboard stimuli subtending 11' and 42' of visual arc. Attention was paid to PERG and PVEP variables used for clinical assessments. The findings confirmed the need to take refractive errors into account because, in some cases, latencies and particularly PERG amplitudes fell outside normal limits with decreased VA, especially when using smaller checks.