BACKGROUND Optic neuropathy is a disorder characterised by dysfunction or destruction of the optic nerve tissues. Acquired causes include interruption in the blood supply, nutritional deficiency, compression by a tumour or aneurysm, trauma, and toxic types (Ambizas and Patel In US Pharm 36(4):HS2-HS6, 1). Drug-induced optic neuropathy is of the toxic type and can be defined as a clinical syndrome characterised by papillomacular bundle damage, central, or cecocentral scotoma, and reduced colour vision (Ambizas and Patel In US Pharm 36(4):HS2-HS6, 2011; Sharma and Sharma In Indian J Ophthalmol 59(2):137-141, 2). OBJECTIVE To report a case unilateral optic neuritis, secondary to the use of the antiandrogen, cyproterone acetate. METHODS A 21-year-old female presented with a 4-day history of right brow pain exacerbated by eye movement, and blurring of the right temporal field of vision. She had been taking desogestrel 75 mg and cyproterone acetate 50 mg for the previous 2 months for hormone imbalance. Unaided right visual acuity measured 6/9 and unaided left visual acuity measured 6/6 on Snellen chart. Right red desaturation was present. Goldmann perimetry showed a right enlarged blind spot with predominantly temporal visual field loss. Visually evoked potential (VEP) testing of the right eye showed slightly increased latency, but normal amplitude. Three weeks after discontinuation of the antiandrogen therapy, her symptoms resolved. Repeat Goldmann visual fields showed expansion. CONCLUSIONS Known side-effects of cyproterone acetate include retinal vascular disorder and retinal vein thrombosis, but an association with optic neuritis had not been described to date. There was a temporal relationship between cessation of the medication and improvement in visual symptoms. This implies that discontinuation of the offending drug constitutes the basis of treatment in drug-induced optic neuropathy.