A Case of Vigabatrin Induced Symptomatic Visual Field Defect

ABSTRACT

Vigabatrin (VGB) is one of the most frequently prescribed new anti-epileptic drugs in the world since 1989. It has minimal side effects and fewer drug interactions with other anti-epileptic drugs. Recently, concern of the prevalence and pathophysiology of visual impairment with VGB has been increased since the reports of visual field constriction in patients treated with VGB. We report a 46-year-old man with a visual field defect who has been suffering from complex partial seizures for 29 years. Brain magnetic resonance image (MRI) and electroencephalogram (EEG) were non-specific. The frequency of seizures was about 5 times a month for the past 5 years. VGB, in a dose of 1500 mg/day, was prescribed as an add on drug in addition to carbamazepine. 19 months after VGB treatment, the patient complained of visual dimness especially in the lower half of the visual field. He expressed it as "waving". He had no metabolic derangement. Fundus examination, visual evoked potential, and electroretinogram showed normal findings. A visual field analysis showed a bilateral field defect in the lower half. A follow up visual field analysis, 6 months after the withdrawal of VGB, revealed a slight improvement of visual field defects which were noted without significant clinical improvement. This case implicates that visual field defects due to VGB may be partially reversible.