Primer on visual field testing, electroretinography, and other visual assessments for patients treated with...

Vigabatrin, an irreversible inhibitor of γ-aminobutyric acid transaminase, is an antiepileptic drug indicated in the United States as adjunctive therapy for adult patients with refractory complex partial seizures who have responded inadequately to several alternative treatments and for monotherapy treatment of infantile spasms in patients 1 month to 2 years of age. Approval of vigabatrin in the United States was contingent on the implementation of a Risk Evaluation and Mitigation Strategy (REMS) to manage the threat of a progressive, permanent bilateral concentric peripheral visual field defects (pVFDs) that may occur in patients treated with vigabatrin. The REMS is designed to promote compliance with evidence-based recommendations for baseline (within 4 weeks of the start of treatment) ophthalmologic evaluations and ongoing vision monitoring in all patients treated with vigabatrin. In view of the challenges associated with visual field testing in patients with epilepsy and in infants, clinicians must understand the qualitative (pattern of damage), quantitative (degree of damage), electrophysiologic, and adjunctive techniques recommended for monitoring vigabatrin-treated patients. The objectives of ongoing research are to characterize the onset, progression, and risk of developing vision loss during the first year of vigabatrin treatment and to evaluate the potential of noninvasive imaging as a method for monitoring retinal changes corresponding to the pVFD. This article provides an overview of visual field testing procedures and electroretinography, summarizes the clinical characteristics of vigabatrin-associated pVFDs, and provides recommendations for visual field and visual electrophysiology testing relevant to both adult and infant patients treated with vigabatrin.