Concentric visual field restriction under vigabatrin therapy: extent depends on the duration of drug intake

Vigabatrin (VGB) is a novel antiepileptic drug which inhibits GABA-transaminase (GABA-T) and thus increases the level of GABA in the CNS and in its neurons. In the last few years, evidence has been presented that VGB intake may be associated with concentric visual field restrictions. The aim of this study was to estimate the prevalence of visual field constrictions and to determine if, and to what extent, they depend on the duration of VGB treatment. Visual fields of 15 patients who were taking VGB, and 12 matched control patients who had never been exposed to VGB, were investigated using a kinetic Goldmann perimeter. One of the 12 matched control patients had a slightly restricted visual field whereas nine of the 15 VGB patients (60%) showed a moderate to severe concentric visual field restriction. The extent of the outer isopters (V4, I4, I3, I2) depended on the duration of VGB intake. VGB treatment was clearly associated with a high prevalence of concentric visual field restriction. Moreover, the degree of visual field restriction depended on the duration of VGB intake. Further work, including longitudinal studies, is needed to clarify whether these lesions are reversible or not.