Visual evoked cortical and subcortical potentials in human albinos.

Albinism is a congenital condition in which hypopigmentation occurs. In addition to this abnormality there is a misrouting of the optic nerve fibers, with some fibers from the temporal retina following a crossed route at the chiasma and terminating in the contralateral cortical hemisphere. This contralateral preponderance of fibers from each eye should be recognizable from recording the visual evoked cortical potential over each hemisphere on monocular stimulation. Such a technique should produce evidence of responses of either increased amplitude or shorter latency over the contralateral hemisphere. Twenty-five human albinos (twenty-three oculocutaneous, two ocular) have been examined. Pattern appearance-disappearance visual evoked cortical potentials were used, but only on bioccipital derivations did these show clear lateralization. With the flash response the P2 component has a consistently shorter latency over the contralateral hemisphere to the eye stimulated. The visual evoked subcortical potential shows contrasting lateralization. The implications of these findings are discussed.