Macular Vessel Density as Early Biomarker of Subclinical Ethambutol-Induced Optic Neuropathy: An OCTA based Cohort Study

Ethambutol is an essential component of Anti-Tubercular Therapy (ATT) but is associated with dose-dependent optic neuropathy. Aim: To detect subclinical ethambutol-induced optic neuropathy (EON) by evaluating macular vessel density (mVD) and structural retinal changes. Methods: A cohort study of 30 patients receiving ATT was conducted. Ophthalmic examinations and OCT/OCTA imaging (mVD, mGCIPL, and pRNFL) were performed at baseline and after six months. Results: 56.7% of patients experienced decreased visual acuity. OCTA analysis revealed a statistically significant decrease in mVD in the affected group (p = 0.021). However, structural changes in macular Ganglion Cell?Inner Plexiform Layer (mGCIPL) and peripapillary Retinal Nerve Fiber Layer (pRNFL) did not reach statistical significance (p > 0.05). Conclusion: Macular vessel density (mVD) serves as a more sensitive biomarker than traditional structural thickness for the early detection of subclinical Ethambutol toxicity. These findings facilitate timely clinical intervention and dosage adjustment to prevent irreversible vision loss in tuberculosis patients.