Vigabatrin Visual Field Defect — SCE Neurology MCQ

Correct answer: B — Functional visual loss with internally inconsistent perimetry

The best answer is “Functional visual loss with internally inconsistent perimetry”. Vigabatrin can cause irreversible concentric field loss, often unnoticed until advanced; baseline and periodic visual-field assessment and prompt specialist drug review are required. “Central retinal vein occlusion with widespread retinal haemorrhage” is less appropriate because optic neuritis is commonly painful and causes colour and central visual dysfunction “Demyelinating optic neuritis with painful central visual loss” is less appropriate because papilloedema produces disc swelling and indicates raised pressure “Vigabatrin retinal toxicity with concentric field constriction” is less appropriate because vein occlusion causes acute monocular loss with retinal haemorrhages “Papilloedema from chronically raised intracranial pressure” is less appropriate because preserved central acuity does not make objectively measured peripheral constriction functional

Reference: Sabril 500 mg tablets: SmPC. https://www.medicines.org.uk/emc/product/4279/smpc