ATT induced asymmetric bilateral toxic optic neuropathy with unilateral visual loss: A case report

ABSTRACT

Toxic optic neuropathy is a known complication of anti-tubercular therapy, particularly with drugs such as ethambutol and linezolid. It commonly presents as bilateral, painless, progressive visual loss. A 22-year-old female presented with painless progressive diminution of vision in the left eye following completion of anti-tubercular therapy for drug-resistant tuberculosis, which included ethambutol and linezolid. Best corrected visual acuity was 6/6 in the right eye and finger counting at 1 meter in the left eye. Color vision and contrast sensitivity were reduced in the affected eye. Fundus examination revealed temporal pallor of the left optic disc. Optical coherence tomography demonstrated left eye temporal retinal nerve fiber layer thinning, while Humphrey Visual Field analysis showed central scotoma. Magnetic resonance imaging of the brain and orbit was unremarkable. Based on the clinical profile and treatment history, a diagnosis of toxic optic neuropathy secondary to combined ethambutol and linezolid toxicity was made. This case highlights an asymmetric bilateral presentation of anti-tubercular drug-induced toxic optic neuropathy and emphasizes the importance of baseline and periodic ophthalmic evaluation in patients receiving prolonged therapy for drug-resistant tuberculosis.