Visual evoked potentials in Leber's hereditary optic neuropathy

Pattern‐reversal visual evoked potentials (VEPs) were measured serially in two brothers with Leber's hereditary optic neuropathy during the active phase of the disease. VEP latency and configuration were normal prior to the onset of visual symptoms. The earliest abnormalities consisted of either prolongation of VEP latency or unusual VEP morphology characterized by a double positive peak. As visual acuity declined progressively over a period of months, there was a parallel progressive prolongation of VEP latency accompanied by less consistent diminution of VEP amplitude. In two eyes, VEP ultimately could no longer be measured. VEP latency was normal in most of the asymptomatic family members, including the maternal presumptive carrier. These findings suggest that VEP measurements do not distinguish the presymptomatic or carrier states but do permit quantitative assessment of the activity and progression of the disease.