Visual field loss associated with vigabatrin: Quantification and relation to dosage

Purpose: To describe the correlation between visual field loss and the dura tion, dosage. and total amount of vigabatrin (VGB) medication in a group of patients with epilepsy. Co-medication of antiepileptic drugs (AEDs) and co mpliance were also studied. Methods: Ninety-two patients (53 male and 39 female) taking VGB medication in the past or the present, attending the Outpatient Epilepsy Clinic in Utr echt, were examined with the Goldmann perimeter. The amount of visual field loss was calculated by the Esterman grid method and by a new method, with which the percentage surface loss of the visual field is measured. A comple te drug history was compiled, specifying the amount and duration of VGB med ication. Concomitant AED medication was noted. Serum levels of AEDs were de termined. Results: Linear regression showed the total amount of VGB as the most signi ficant parameter to predict visual field loss (p < 0.001). Further, men wer e more affected than women (p = 0.026). Compliance was good, and other AEDs did not influence the results. Conclusions: Because prolonged use of VGB medication is correlated with the amount of visual field loss, VGB should be prescribed only when there are no alternatives. In such cases, we recommend an examination of the peripher al visual field before starting therapy and a repeated examination every 6 months.