Study of VEP in Ethambutol Optic Neuropathy: A Cross-sectional Study

Abstract

Introduction: One important first-line drug for treating Tuberculosis (TB) is Ethambutol (EMB), which carries a built-in risk of causing optic neuropathy, potentially resulting in permanent visual impairment. The subjective tests currently used in the diagnostic process, such as visual acuity and visual field assessments, may overlook early changes in visual function. The purpose of the present study is to investigate how well Visual Evoked Potentials (VEP) work as an evaluation tool for identifying optic neuropathy. Aim: To assess the utility of VEP in detecting subtle changes in visual function due to EMB-induced optic neuropathy. Materials and Methods: The cross-sectional study conducted at the Department of Physiology, B.J. Medical College, Ahmedabad, Gujarat, India, over approximately five months (August 2023 to December 2023) involved 62 eyes, with 30 eyes from TB patients undergoing EMB treatment and the rest serving as a control group. VEP recordings were made using a Personal Computers (PC)-based, 2-channel Recorders & Medicare Systems Pvt Ltd Nerve Conduction Velocity (NCV) Electromyography (EMG) Mark II machine with standard silver-silver chloride disc electrodes. VEP recordings were conducted regardless of the treatment period and the analysis focused on the amplitude and latency of the P100 wave, a critical component of VEP. Statistical analysis was carried out using Student’s unpaired t-test to compare the results between both groups, with p-values calculated. Results: The mean age of case was 40±17.4 years and controls was 31.12±12.54 years. The study revealed changes in VEP parameters, specifically showing a progressive reduction in P100 amplitude (p-value=0.0001). Conclusion: The present research highlights the potential of VEP as a sensitive and reliable method for assessing EMB-induced optic neuropathy. Incorporating VEP into routine ophthalmologic assessments for patients receiving EMB could improve TB management while reducing the risk of vision loss.

Keywords

• flash visual evoked potential
• pattern visual evoked potential
• visual evoked potential