# Longitudinal Observation by Optical Coherence Tomography in Patients Treated with Ethambutol: A Systematic Review and Meta-Analysis

## TL;DR

This study finds that ethambutol treatment does not generally cause retinal nerve fiber layer thinning in mycobacterial infection patients, though some subgroups like males show significant changes.

## Contribution

The study provides a meta-analysis of OCT measurements to clarify ethambutol's effects on retinal layers in patients without optic neuropathy.

## Key findings

- Ethambutol does not cause significant retinal nerve fiber layer (RNFL) thinning overall in patients without EON.
- Male-dominant studies and those in Turkey and India show significant RNFL thickness decreases.
- Only two studies reported GCIPL thickness changes, with significant decreases in male-dominant studies.

## Abstract

Background: The retinal changes caused by ethambutol are not clear in patients with the administration of ethambutol and without ethambutol-induced optic neuropathy (EON). The aim of this systematic review is to estimate the changes in retinal nerve fiber layer (RNFL) and ganglion cell layer and inner plexiform layer (GCIPL) thicknesses measured by optical coherence tomography (OCT) in patients with mycobacterial infection treated with ethambutol and not suffering from EON. Methods: A systematic review of articles was conducted by searching PubMed, Embase, and Web of Science until November 2025. Additional studies were identified by the review of references. Search terms included OCT and ethambutol. Longitudinal observational studies using an OCT device to measure RNFL and GCIPL thicknesses before and after the administration of ethambutol in patients with mycobacterial infection without ocular diseases were included. The extraction of data in studies was performed by two researchers using data extraction sheets. The meta-analysis was conducted using the random-effect model. Results: In total, 14 studies (n = 1138) were eligible for the systematic review. Meta-analysis combining RNFL measured after the longest duration of ethambutol administration showed no significant decrease compared to RNFL before treatment. However, there were significant decreases in RNFL thickness in male-dominant studies, studies conducted in Turkey and India, and studies conducted by the Cirrus OCT device. In addition, the decreases in RNFL thickness were correlated with the duration of ethambutol administration in male-dominant studies. Only two studies reported the thickness changes in GCIPL, and the study with a higher male proportion showed significant decreases in GCIPL thickness. Conclusions: Ethambutol does not cause a significant RNFL decrease generally in mycobacterial infection patients; however, it may lead to decreased RNFL thickness in male patients and patients in some regions, even though they do not suffer from EON.