Isoniazid and ethambutol as a cause of optic neuropathy.

A well-recognized complication of ethambutol use is optic neuropathy, but the potential ocular toxicity of isoniazid is often overlooked. A patient developed optic neuropathy while being treated with isoniazid and ethambutol. The optic neuropathy subsided only when both drugs were discontinued, suggesting an additive toxic effect.