Vigabatrin-attributable visual field defects in patients with intractable partial epilepsy

Introduction: Vigabatrin (VGB) is implicated to cause visual field defects. We estimated the prevalence, described the characteristics and investigated the risk factors of VGB-attributable visual field defects. Methods: Patients with intractable partial epilepsy under VGB add-on treatment received static perimetric examinations. Visual field charts were reviewed and interpreted using a three-grade system. Clinical features and therapeutic courses were analyzed for possible risk factors. Results: Visual field defects in at least one eye were detected in 27 (79%) of 34 patients. In the subgroup of 27 patients with both eyes reliably tested, 16 (59%) had bilateral defect, among whom seven were severely involved and showed nasally dominant, crescent or concentric defect. Five patients had unilateral visual field defects. Four out of the 27 affected patients reported blurred vision. No statistically significant differences were noted between patients with and without visual field defects in terms of gender, age, duration or etiology of the epilepsy, and duration, maximum daily dose, or cumulative dose of VGB. Conclusions: There was a high prevalence of VGB-attributable visual field defects. No risk factors could be identified. Routine initial and regular follow-up of visual field examination, especially that focusing within a range of central fixation to 60°, should be performed in patients on VGB.