Vigabatrin, a gabaergic antiepileptic drug, causes concentric visual fielddefects

Objective: To determine whether there is a causal link between vigabatrin t reatment and concentric visual field defects and to evaluate the prevalence of these visual field constrictions. Background: While the GABAergic antie pileptic drug (AED) vigabatrin was being clinically developed, only rare ca ses (less than 1:1000) of symptomatic visual field constriction and retinal disorders were reported. During 1997 to 1998, concentric visual field cons trictions were described in case reports of mostly drug-resistant epilepsy patients receiving vigabatrin concurrently with other AEDs. Methods: Ophtha lmologic tests including Goldmann perimetry were performed on 32 adult pati ents on long-term successful vigabatrin monotherapy (treatment duration 29 to 119 months) and on 18 patients on carbamazepine monotherapy (treatment d uration 32 to 108 months). Eighteen healthy adults served as controls. Resu lts: None of the patients complained about vision problems when asked to pa rticipate into the study. Thirteen out of the 32 (40%) epilepsy patients tr eated with vigabatrin monotherapy had concentrically constricted visual fie lds (9% severely, 31% mildly constricted), whereas none of the carbamazepin e monotherapy patients or normal controls presented with a visual field def ect (chi-square test, p = 0.0001). The extents of the visual fields were si gnificantly constricted in vigabatrin group as compared with the visual fie lds of the patients in carbamazepine group or healthy controls (analysis of variance, Scheffe F-test, significant at 99%). Conclusions: The use of vig abatrin seems to increase the risk of a unique and specific pattern of bila teral, mainly asymptomatic visual field constriction. This risk should be c onsidered when using vigabatrin. Visual field testing should also be perfor med before treatment and during routine follow-up for patients on vigabatri n.