Visual field constriction as a side effect of GABA-mimetic antiepileptic agent

Bilateral visual field constriction has been recently reported in patients treated with vigabatrin. It has been considered that vigabatrin, a GABA ago nist antiepileptic drug, was specifically responsible for this visual field defect. We present four observations sharing the same characteristics of c hronic tunnel vision. Three patients had had vigabatrin but the fourth one received other antiepileptic drugs, progabide, an agonist of post-synaptic GABA receptors, and phenobarbital which interferes with GABA-A receptors. I t is thus possible to hypothesize a retinal toxicity triggered by chronical ly increased GABA transmission. If this is confirmed, an accurate incidence of symptomatic and asymptomatic visual field constriction with GABA-mimeti c drugs should be established, as well as the patients' profiles which are more at risk. Patients currently under this type of treatment should be che cked by both manual and automatic perimetry every six months to one year.