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.