Optic neuropathy induced by ethambutol: A rare case from Nepal.

Introduction: Ethambutol is a drug used against tuberculosis and causes side effects like problems with vision, which may lead to optic neuropathy. It has a low prevalence of 1% and typically develops after 4-12 months of its medications.

Case Presentation: Here, we report a case of a 42-year-old male with ethambutol-induced optic neuropathy after six weeks of initiations of ethambutol.

Discussion: Nutritional and tobacco/alcohol, ischemia, compressive, demyelinating, and genetic optic neuropathies were all ruled out as differential diagnosis for toxic optic neuropathy. Because our patient did not have vasculopathy and his vision loss was progressive on follow up and bilateral, rather than acute and unilateral, as is more usual with an ischemic disease, ischemic optic neuropathy was ruled out. Finally, because hereditary optic neuropathy usually manifests at a younger age and is expressed in many generations which was not the case in our patient, it was effectively ruled out as the cause of optic neuropathy.

Conclusion: This case highlights that ethambutol toxicity is rare in cases of new onset pulmonary tuberculosis where ethambutol has been administered for only 2 months.