Visual function is stable in patients who continue long-term vigabatrin therapy: implications for clinical decision making.

PURPOSE: Vigabatrin (VGB) has been shown to cause visual field constriction and other forms of mild visual dysfunction. We determined the safety of continuing VGB therapy in patients who had received prolonged treatment (>2 years) with the drug by serially monitoring changes in visual function over a 1-year period of continued therapy. We also followed up patients who discontinued VGB to see whether alternative therapies are effective.
METHODS: Fifteen of 17 patients who continued VGB therapy had visual-function testing (visual acuity, color vision, kinetic and static perimetry) every 3 months for 1 year. Eighteen patients who discontinued VGB were given alternative antiepileptic drugs (AEDs); their seizure responses were measured after > or =3 months of treatment.
RESULTS: Patients continuing VGB showed no worsening of visual acuity, color vision, or visual-field constriction beyond that measured in the initial test. Many patients who discontinued VGB had good seizure control with either newer or previously unsuccessful AEDs.
CONCLUSIONS: For patients who have an excellent response to VGB and only mild visual changes, continued therapy may be safe with close visual monitoring. Patients who do not have a significant reduction in seizures or who experience considerable visual dysfunction with VGB may respond well to alternative therapies.