Visual evoked potential as an early assessment tool in ethambutol-induced toxic optic neuropathy during treatment of tuberculosis

Abstract

The objective of this study was to determine whether visual evoked potential (VEP) may be utilized as a screening tool for Ethambutol-induced toxic optic neuropathy (EITON) and whether discontinuing the use of Ethambutol will reverse the signs and symptoms of EITON in patients who are suffering from tuberculosis.Following receipt of authorization from the Institutional Ethics Committee to proceed with the present study, the study officially got underway. The World Health Organization recommended that forty people who had been diagnosed with tuberculosis get ethambutol medication for a period of six months at a dosage of 15-19 milligrams per kilogram of body weight. These patients were inspected both before and after receiving the treatment. Visual function tests and visual evoked potential (VEP) tests were administered to each patient to assess the visual pathway's condition.An irregular VEP pattern was seen in seven patients out of forty individuals, which accounts for 17.5% of the total. Among these seven patients, delayed P100 latency was observed in all seven patients (17.5%), and an aberrant amplitude difference was documented in one patient (2.5%). There were four patients (10%) who were found to have suboptimal visual acuity, and there were three patients (7.5%) who were found to have problems with their colour vision. An association between low visual acuity and increased P100 delay values was discovered in three out of seven cases. This was the case that was investigated. One patient's visual acuity and colour vision had decreased after two months of Ethambutol therapy, while three patients' visual acuity and colour vision had decreased within four to six months of medication. Due to the absence of abnormalities in the fundus, a diagnosis of retrobulbar optic neuritis was made in these four cases, constituting 10% of the total. There was a full reversal of P100 delay in three patients (43%) out of seven and a partial reversal in four (57%) out of seven.Our study demonstrates that even at the recommended doses of ethambutol, a timely and routinely performed pattern VEP can detect a significant proportion of cases of subclinical optic neuritis. Furthermore, it demonstrates that the signs and symptoms of ocular toxicity can be reversed in a significant number of these patients after the cessation of Ethambutol treatment.