Ethambutol toxic optic neuropathy

Irimpan Lazar FRANCIS ¹, Ramalingam MOHAN ¹, Nayan JOSHI ¹, Nadir Ali MOHAMAD ALI ¹, Allimuthu NITHYANANDAM ²

¹ Department of Ophthalmology, RIPAS Hospital, and ² Division of Neurology, Department of Medicine, RIPAS Hospital, Bandar Seri Begawan, Brunei Darussalam

ABSTRACT

Ethambutol is a commonly used anti-tuberculous medications. Ocular toxicity of ethambutol is well established. It needs to be detected early and medication stopped promptly to avoid irreversible damage. A 64-year-old lady was referred for gradual deterioration of her vision of both eyes. Examination and investigations confirmed bilateral toxic optic neuropathy secondary to ethambutol. The drug was stopped with immediate effect. Three months later, her distance vision and colour vision improved  significantly. The course and outcome of ethambutol induced toxic optic neuropathy is unpredictable. Optic nerve head remains normal on Fundoscopy until late in the disease. Improvement of vision after discontinuation of ethambutol occurs only in a minority of patients. This case highlights the importance of ocular screening to detect toxic neuropathies early to possibly prevent permanent visual disability.

Keywords: Ethambutol, dyschromatopsia, scotoma, optic neuropathy

Brunei Int Med J. 2013; 9 (6): 385-389