Visual functions in epilepsy patients on valproate monotherapy.

Gamma-aminobutyric acid-induced ion transport changes in the retinal pigment epithelium are described. Valproate acts as an inhibitor of gamma-aminobutyric acid transaminase. The purpose of this study was to investigate whether early visual impairment is related to valproate in patients with and without visual symptoms. Thirty-two patients, presenting with a history of seizures currently being treated with valproate, were included in the study. A complete clinical neuroophthalmologic examination was performed, including electroretinogram and visual field test. The electroretinogram parameters of epileptic patients were compared with those of 28 age- and sex-matched healthy volunteers. There was no significant difference in ERG parameters between the two groups. The visual field and visual acuity of all patients were within normal limits. When valproate is not used in conjunction with other antiepileptic drugs and serum levels are within therapeutic levels, it does not cause electrophysiologically detectable retinal dysfunction or any functional defect in visual perception that can be determined clinically. Copyright 2002 Published by Elsevier Science Ltd.