Ethambutol Toxicity: Jekyll and Hyde of Ethambutol

Ethambutol is a drug commonly used in the treatment of tuberculosis, a systemic disease that is widespread in our country. It is known to cause ocular toxicity which may cause impaired vision, sometimes reversible, and at times may result in permanent loss of vision. Diagnosis of its toxicity is mainly a diagnosis of exclusion. As stopping an essential antitubercular drug can be detrimental to the management of tuberculosis, we must be careful and sure before stopping ethambutol. Here we present three cases with ethambutol optic neuropathy: one of which had coexisting glaucoma making it difficult to rule out ethambutol toxicity. The acuteness of symptoms along with a panel of tests including visually evoked potential, OCT RNFL, color vision, and visual fields along with MRI brain and orbit helped us to narrow it down to the cause of ocular impairment.