Visual field defects in patients taking vigabatrin

PURPOSE: To investigate visual field loss in patients on long-term treatment with the antiepileptic drug vigabatrin, recently reported to cause visual disturbances. METHODS: Eighteen patients taking vigabatrin for 0.5-9.5 years were examined with automated perimetry up to 60 degrees from fixation using the Humphrey Field Analyser. Five patients with epilepsy receiving other medications served as controls. Patients found to have a visual field defect underwent ophthalmologic examination. RESULTS: Among the 18 patients in the vigabatrin group, visual field defects categorised as mild were revealed in 6 right eyes (33%) and 8 left eyes (44.4%), while defects categorised as severe were found in 9 right eyes (50%) and 8 left eyes (44.4%). The majority of the defects (66.7% in the right eye) were peripheral constriction with nasal predominance. The location of the defects was confirmed in 8 patients also tested with Kowa AP340 perimetry. CONCLUSION: According to our results, visual field defects among the patients on vigabatrin therapy may occur more frequently than previously recognised.