Dissociation of damage to spatial and luminance channels in early Leber's hereditary optic neuropathy manifested by the visual evoked potential.

Leber's hereditary optic neuropathy (LHON) is a maternally inherited disorder characterised by the acute or subacute loss of central vision, leading to severe optic atrophy. The occurrence of a demyelinating disease such as multiple sclerosis (MS) has been reported mainly in females with the mitochondrial DNA 11778 mutation. They had a poor visual outcome. To investigate the damage to the optic nerve in an early stage of LHON as compared with optic neuritis (ON), including MS, we examined patients by testing their pattern visual evoked potential (PVEP) and flash VEP (FVEP). The mean amplitude and latency in the PVEP were reduced and delayed, respectively, in patients with LHON or ON. The mean amplitude in the FVEP was reduced in patients with LHON or ON, but the mean latency was not delayed in patients with LHON as compared with normal subjects or patients with ON. Luminance-related fibres may be less affected than are the spatial-vision-related fibres in patients with early LHON.