Visual Functions in Patients With Leber Hereditary Optic Neuropathy (LHON).

Background: Most of the data on visual functions in Leber hereditary optic neuropathy (LHON) is based on patient questionnaires. Our study assessed the impact of LHON on visual function by testing facial recognition and execution of purposeful actions.

Methods: Twelve participants with LHON with central scotoma ranging from 5° to 20° and 12 unaffected age-matched controls were involved in our study. In the face recognition test, participants were asked to recognize the sex and the facial expression of photographs of faces increasing in size to simulate approaching faces. In the purposeful action test, they were asked to manipulate real objects while their eye movements were recorded.

Results: Although most patients were able to recognize the correct sex of a face at a size corresponding to a 1-m viewing distance, recognition of facial expressions was severely impaired. Patients were slower than control subjects in executing purposeful tasks. A dynamic strategy to sample information needed for the execution of a task was documented in a longer scanpath and in higher frequency of saccades and fixation eye movements in patients than in control subjects.

Conclusions: Face perception is strongly impaired in patients with LHON. In addition, although the selection and manipulation of real objects to execute a task are slowed, they can be performed efficiently using peripheral vision.