Saxena Rohit
Dr. R P Centre for Ophthalmic Sciences,
AIIMS, New Delhi, INDIA.
Abstract
Ethambutol is a major component of anti-tubucular treatment due to its good anti‑mycobacterial action, low incidence of resistance and relative systemic safety. However, it may lead to permanent vision loss by inducing a dose‑ and duration‑ dependent opticneuropathy which is a major concern to ophthalmologists and physicians. Recently, Revised National Tuberculosis Control Programme of India guidelines have recommended fixed dose and longer duration of ethambutol use which may potentially result in increase in vision‑ threat eningadverse effects. There is no effective treatment of ethambutol toxicity except stopping the drug and vitamin supplementation to prevent further damage and help in visual recovery. Damage is reversible if the drug is stopped early at the time of onset of toxicity. As primary prevention is the best way to prevent ethambutol opticneuropathy, it is essential to make health care workers at all levels aware of the side effect of the drug. To increase awareness among patients and health care providers written instructions or education pamphlets can be provided to physicians, fieldworkers and patients. It is important to identify high-risk individuals (patients with co-morbidities like renal function impairment, Diabetes Mellitus, those with tobacco/alcohol abuse, on combined therapy with Linezolid, pre-existing visual dysfunction and young /preverbal children), those receiving higher doses (low weight in weight band) and patients receiving for longer duration (Drug resistant TB). Ideally, each patient should undergo baseline ophthalmic evaluation before commencement of the treatment followed by regular evaluation of visual acuity, colour vision and visual fields. However, in countries with high disease burden, as it may not be practical to perform these tests in all patients on ethambutol, patients with high risk factors should undergo baseline ophthalmice valuation and at every 2 month follow-up visits while patients without high risk should undergo screening at 3 and 6 months follow-up visits.