Comment on: Ethambutol toxicity: Expert panel consensus for the primary prevention, diagnosis, and management of ethambutol-induced optic neuropathy.

Dear Editor,

I went through the article titled “Ethambutol toxicity: Expert panel consensus for the primary prevention, diagnosis, and management of ethambutol-induced optic neuropathy” by Saxena et al.[1] This consensus statement is a very helpful document for physicians and ophthalmologists in preventing potential cases of ethambutol-induced toxic optic neuropathy. The expert panel has stressed on the importance of baseline ophthalmic examination. Unfortunately, the major stumbling block in preventing ethambutol toxicity is a lack of awareness among the patients. We regularly receive patients in our OPD for a baseline screening before starting a drug like hydroxychloroquine but we hardly receive patients for a baseline screening before initiating antitubercular therapy containing ethambutol. In fact, in my short career as a vitreoretinal consultant spanning a decade, I have not been referred a single patient for a baseline ophthalmic examination before starting ethambutol. Most of the time when a patient comes to us, a gross decrease in vision has already happened. Majority of cases of ethambutol-induced optic neuropathy are not even aware that a regular ophthalmic examination is needed throughout the course of therapy. All this highlights a failure on part of healthcare providers in adequately educating the patients. The patients need to be made aware of the fact that repeated ophthalmic examinations throughout the course of the therapy are as important as getting regularly examined by the primary physician. Baseline ophthalmic examination is at least needed in patients with high-risk factors like renal disease, elderly age, low body weight, and chronic smokers. Patients requiring ethambutol throughout the course of the disease should have both baseline and follow-up ophthalmic examinations at regular intervals.

Majority of the patients with active tuberculosis are from the rural background. In many cases, though the primary diagnosis may be made at a peripheral center, the patients usually are dependent on the primary health center to get their medications. The consensus document has stressed on simple ophthalmic examinations like assessment of visual acuity, color vision, and contrast sensitivity in patients on ethambutol. A self-assessment using smartphone applications is also a very good suggestion. However, many patients with rural background might not have either access to smartphones or might find difficulty in operating them. It will also not be feasible to equip all primary health centers with advanced investigation facilities like optical coherence tomography. All these peripheral centers should be at least equipped with vision charts, color vision and contrast sensitivity charts and the paramedical staff posted in such centers should be trained to use these charts. They should also be trained to educate the patients and inform them to consult immediately at the slightest drop in vision.

Toxic optic neuropathy due to ethambutol is preventable. Creating simple awareness at multiple levels will go a long way in preventing vision loss due to its toxicity.

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