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Vigabatrin-Associated Visual Field Defect — SCE Neurology MCQ

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ModerateNeuro-ophthalmologyVigabatrin-Associated Visual Field DefectSCE Neurology

A 45-year-old man presents with painless progressive bilateral visual field constriction over 2 years. He is on vigabatrin for refractory focal epilepsy. Goldmann perimetry shows bilateral concentric visual field constriction with preserved central acuity. What is the most likely cause?

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Correct answer: D — Vigabatrin-associated visual field defect

Vigabatrin causes an irreversible concentric visual field defect in approximately 30–40% of patients on long-term therapy. It is due to retinal toxicity (GABA accumulation in retinal cells). The visual field loss is typically bilateral, concentric, and nasal-predominant, with preserved central acuity. Regular perimetric monitoring (every 6 months) is mandatory for all patients on vigabatrin. A: Glaucoma causes arcuate field defects, not concentric constriction. C: Optic neuritis causes central scotoma. D: RP causes ring scotoma with bone spicule pigmentation. E: Papilloedema causes enlarged blind spots.

Reference: NICE NG217 (2025); BNF – Vigabatrin; Vigabatrin SmPC