Visual field defects in patients taking vigabatrin

Purpose: To investigate visual field loss in patients on long-term treatmen t with the antiepileptic drug vigabatrin, recently reported to cause visual disturbances. Methods: Eighteen patients taking vigabatrin for 0.5-9.5 years were examine d with automated perimetry up to 600 from fixation using the Humphrey Field Analyser, Five patients with epilepsy receiving other medications served a s controls. Patients found to have a visual field defect underwent ophthalm ologic examination. Results: Among the 18 patients in the vigabatrin group, visual field defect s 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 perimet ry. Conclusion: According to our results, visual field defects among the patien ts on vigabatrin therapy may occur more frequently than previously recognis ed.