Abstract
To describe the optical coherence tomography (OCT) and electrophysiological changes in a case of closantel toxicity. A 25-year-old patient presented with sudden painless defective vision following intake of closantel. Visual acuity (VA) was counting fingers at 5 m in both eyes (BE). OCT revealed disruption of outer retinal layers and electroretinogram (ERG) and visual evoked potential (VEP) were subnormal in BE. The patient was treated with systemic corticosteroids, after which his VA improved to 6/9, OCT revealed preservation of central outer retinal layers, and ERG and VEP responses improved in BE. This is the first case report of successful treatment with systemic steroids for closantel-related reversible blindness.