Purpose: To describe two patients who presented with severe campimetric constriction and to determine the source of visual symptoms caused by vigabatrin, an anticonvulsant medication that increases brain gamma-aminobutyric acid. Methods: Patients were submitted to a complete neuroophthalmologic evaluation as well as a careful retina examination, Goldmann perimetry, computerized tomography of the brain and orbits, electroretinograms (ERG), magnetic ressonance imaging (1 patient) and visual evoked potential (1 patient). Results: Visual acuity was normal; the first patient had the visual field restricted to the 20 to 30 degree central area and the second, a mild to moderate constriction. Neuroimaging examinations were normal as well as the visual evoked potential. Mild optic disc pallor (3 eyes) and very slight retinal arteriolar narrowing was observed. ERG showed reduction of the b wave (case 1) and oscillatory potential responses (case 2). Conclusions: Visual alterations caused by vigabatrin are due to a retina dysfunction presumably involving the amacrine, bipolar and ganglion cells but there are no significant pathologic findings on fundoscopic examination. Patients receiving this medication should be followed closely with periodic central and peripheral visual field testing.
Vigabatrin; Visual fields; Electroretinogram
