Multifocal electroretinography changes in patients on ethambutol therapy

Area of Science:

• Ophthalmology
• Neuroscience
• Pharmacology

Background:

• Ethambutol is a first-line antituberculosis drug.
• Ocular toxicity is a known side effect of ethambutol.
• Subtle visual pathway changes may precede clinical symptoms.

Purpose of the Study:

• To investigate multifocal electroretinography (mfERG) changes in patients receiving ethambutol therapy.
• To assess for subclinical visual dysfunction in ethambutol-treated individuals.

Main Methods:

• A cross-sectional study compared 17 visually asymptomatic patients on ethambutol with 17 controls.
• Ophthalmic examinations and mfERG recordings were performed.
• mfERG N1 and P1 amplitudes and implicit times were analyzed and correlated with ethambutol dosage and duration.

Main Results:

• No significant differences in mfERG N1 and P1 response amplitudes were found between groups.
• Significant delays in mfERG P1 implicit times were observed in the peripheral macula (rings 4-6) of the ethambutol group.
• No significant correlation was found between mfERG parameters and ethambutol usage metrics.

Conclusions:

• mfERG suggests mild, localized electrophysiological changes in the peripheral macula of ethambutol-treated patients.
• These findings may reflect localized metabolic or physiological alterations due to ethambutol.
• mfERG may serve as a sensitive tool for detecting early, subclinical ocular effects of ethambutol.