Masquerading Cases of Ethambutol-Induced Toxic Optic Neuropathy

Purpose: We report rare cases of ethambutol-induced optic neuropathy that masquerades as age-related disorders. Case summary: (Case 1) A 90-year-old man with moderate dementia presented with bilateral progressive visual disturbance. Visual acuities were hand motion (OD) and 4/200 (OS), both not corrected. Hypermature cataract (OD) and thick nucleosclerosis (OS) were observed. Cataract surgery was performed in both eyes. Visual acuity and mental status improved after the operation, but degraded after 3 months. Ocular findings were non-specific, but he was being treated for tuberculosis pleurisy since a year ago. Visual acuity improved after cutting ethambutol, and was 8/20 (OU) after 5 years. (Case 2) A-76-year-old woman presented with decreased vision of both eyes. She had been diagnosed with pulmonary tuberculosis 5 months prior to the visit. Follow-up had been lost since then. Progressive cataract was suspected and operation was performed, with no improvement. Visual field exam revealed scotomas, so normal tension glaucoma was also suspected. A two-prong approach of ethambutol discontinuation and antiglaucomatic treatment was initiated, which resulted in progressive but slow improvement of vision. Visual acuity was 20/25 in both eyes 2 months later. Conclusions: Ethambutol treatment in the elderly can masquerade as age-related disorders. As the incidence of atypical tuberculosis is increasing, careful evaluation of tuberculosis is necessary in opthalmology.