Electro-oculography, electroretinography, visual evoked potentials, and multifocal electroretinography in patients with vigabatrin-attributed visual field constriction

Purpose: Symptomatic visual field constriction thought to be associated wit h vigabatrin has been reported. The current study investigated the visual f ields and visual electrophysiology of eight patients with known vigabatrin- attributed visual field loss, three of whom were reported previously. Six o f the patients were no longer receiving vigabatrin. Methods: The central and peripheral fields were examined with the Humphrey Visual Field Analyzer. Full visual electrophysiology, including flash elect roretinography (ERG), pattern electroretinography, multifocal ERG using the VERIS system, electro-oculography, and flash and pattern visual evoked pot entials, was undertaken. Results: Seven patients showed marked visual field constriction with some s paring of the temporal visual field. The eighth exhibited concentric constr iction. Most electrophysiological responses were usually just within normal limits; two patients had subnormal Arden electro-oculography indices; and one patient showed an abnormally delayed photopic b wave. However, five pat ients showed delayed 30-Hz flicker b waves, and seven patients showed delay ed oscillatory potentials. Multifocal ERG showed abnormalities that sometim es correlated with the visual field appearance and confirmed that the defic it occurs at the retinal level. Conclusion: Marked visual field constriction appears to be associated with vigabatrin therapy. The field defects and some electrophysiological abnorma lities persist when vigabatrin therapy is withdrawn.