Dark- and light-adapted visual evoked cortical potentials in retinitis pigmentosa.

Fifty patients with all genetic types of retinitis pigmentosa (RP) were tested with the visually evoked cortical potential (VECP) by full-field flashes of blue and red light in the dark-adapted state and white light flashes in the light-adapted state. VECPs were recorded in all but one of these patients, even those with only a few degrees of central visual field remaining. In a subgroup of patients the absence of the VECP to blue light, dark-adapted, was correlated with a final dark-adapted threshold at or above cone threshold. These observations suggest that the VECP may be a useful objective method of assessment of patients with RP especially patients without detectable ERGs.