Ethambutol-Induced Visual Disturbance: A Case Report Emphasizing Early Recognition and Management

Ethambutol is a key component of first-line antitubercular therapy due to its bacteriostatic activity against Mycobacterium tuberculosis. However, it carries a well-recognized risk of optic neuropathy, which, if not promptly identified, may result in permanent visual impairment. Ethambutol-induced optic neuropathy (EON) is typically dose- and duration-dependent, but cases may also occur at standard dosages in the absence of classical risk factors. We present the case of a 47-year-old male undergoing standard anti-tubercular treatment who developed progressive bilateral visual disturbances—central scotomas, night blindness, and photophobia— approximately six weeks after initiating therapy. He was receiving ethambutol at a dose of 800 mg/day (approximately 15 mg/kg/day). Clinical suspicion of EON led to immediate discontinuation of ethambutol and substitution with levofloxacin. Causality was assessed as “probable” using both the WHO-UMC system and Naranjo’s scale. Although formal ophthalmologic evaluation and follow-up were limited, the temporal relationship, clinical presentation, and dose-response supported the diagnosis. This case underscores the need for heightened clinical vigilance, routine visual monitoring, and patient education—even in cases adhering to standard treatment guidelines. Given the irreversible nature of delayed-detected EON, baseline and periodic ophthalmologic assessments should be integrated into tuberculosis treatment protocols to facilitate early detection and intervention.