Kerala Journal of Ophthalmology (Jan 2021)

Optic nerve head-retinal nerve fiber layer analysis with spectral-domain optical coherence tomography of ethambutol-induced ocular toxicity in patients on a daily regime of anti-tubercular therapy

  • Sanaa Mohammed Konnakkodan,
  • Charmaine Bridgette Solomon,
  • Padma B Prabhu,
  • A Arun Kumar

DOI
https://doi.org/10.4103/kjo.kjo_162_20
Journal volume & issue
Vol. 33, no. 3
pp. 291 – 298

Abstract

Read online

Purpose: This study aims to analyze the clinical profile of patients who presented with visual symptoms after the onset of anti-tubercular therapy (ATT) on daily fixed drug combination and to quantify optic nerve damage in these patients using optical coherence tomography as an objective tool. Study Design and Methodology: This was a cross-sectional observational study of 20 patients who presented with visual symptoms following treatment with daily regime ATT. History was recorded, and detailed ophthalmological evaluation was done, including optic nerve head-retinal nerve fiber layer (ONH-RNFL) analysis using spectral-domain optical coherence tomography (SD-OCT). Data were analyzed with PSPP software. Results: Patients received ethambutol (EMB) at a mean daily dose of 17.61 ± 1.73 mg/kg/day. Of the 40 eyes analyzed, color vision was defective in 35 eyes and contrast sensitivity was reduced in 27 eyes. Mean ONH-RNFL thickness values were 110.8 ± 26.5 μm; 103.7 ± 24.4 μm; 72.6 ± 18 μm; 63.9 ± 13.2 μm; in the inferior, superior, nasal, and temporal quadrants, respectively. Females had more RNFL loss than males. Age, weight, and contrast sensitivity had a positive correlation and log mar vision had a negative correlation with RNFL thickness. Duration of EMB therapy, cumulative dose, and indication for ATT influenced ONH-RNFL thickness. History of renal disease, alcoholism, and smoking were risk factors for RNFL loss. There was a median delay of 21 days in reporting after the development of visual symptoms. Conclusions: Our study population received EMB at a daily dose of >15 mg/kg/day. ONH-RNFL thickness was reduced on SD-OCT. RNFL thickness helps to quantify the role of various risk factors in EMB toxicity, making it a useful tool for objective assessment. Patient education and active screening for the detection of early toxicity are needed to reduce visual impairment and blindness.

Keywords