Prospective study to evaluate incidence and indicators for early detection of ethambutol toxicity.

Abstract

AIMS:

To evaluate incidence of toxic optic neuropathy in patients receiving ethambutol (EMB) for 6 months and to identify its early indicators.

METHODS:

We included 50 patients on anti-tubercular therapy (ATT) including EMB (HRE regimen) based on total body weight for 6 months. Best-corrected visual acuity (ETDRS), colour vision (Ishihara pseudo-isochromatic plates), contrast sensitivity (Pelli-Robson chart), Humphrey visual field analysis (HVF 30-2 SITA FAST), pattern visual evoked response (VER) and spectral-domain optical coherence tomography (SDOCT) for ganglion cell inner plexiform layer (GCIPL) and retinal nerve fibre layer (RNFL) analysis were assessed at baseline and at 2, 4 and 6 months after starting ATT.

RESULTS:

Mean age of the patients was 36.5±14.7 years with male:female ratio of 2.5:1. Mean daily dosage of EMB was 17.5±1.3 mg/kg/day. No significant change was observed in visual acuity, contrast sensitivity, color vision and mean or pattern SD on HVF at 6 months. Significant increase in VER latency of >2 SD (>125 ms) was observed in 46% eyes on follow-up indicating subclinical toxicity. Significant loss of mean RNFL (from 100.79±16.05 μm to 89.96±13.79 μm) and GCIPL thickness (from 83.1±5.60 μm to 79.85±6.45 μm) was observed at 6 months (p=0.001 for both). Patients with subclinical toxicity had significantly greater damage in temporal RNFL quadrant, supero-nasal and infero-nasal GCIPL sectors compared with others.

CONCLUSION:

The incidence of clinical EMB optic neuropathy was <2%, though subclinical damage in the form of increase in VER latency, and decrease in RNFL and GCIPL on OCT was seen in 46% eyes.

• Authors: Sohini Mandal, Rohit Saxena, Rebika Dhiman, Anant Mohan, Srikanta Kumar Padhy, Swati Phuljhele, Pradeep Sharma, Randeep Guleria
• Journal: The British journal of ophthalmology (Br J Ophthalmol) Vol. 105 Issue 7 Pg. 1024-1028 (07 2021) ISSN: 1468-2079 [Electronic] England
• PMID: 32713840 (Publication Type: Journal Article)
• Copyright: © Author(s) (or their employer(s)) 2021. No commercial re-use. See rights and permissions. Published by BMJ.

Chemical References

• Antitubercular Agents
• Ethambutol

Topics

• Adult
• Aged
• Antitubercular Agents (toxicity)
• Color Vision (physiology)
• Contrast Sensitivity (physiology)
• Ethambutol (toxicity)
• Evoked Potentials, Visual (drug effects, physiology)
• Female
• Humans
• Incidence
• Male
• Middle Aged
• Nerve Fibers (pathology)
• Optic Nerve (drug effects)
• Optic Nerve Diseases (chemically induced, diagnosis, epidemiology)
• Prospective Studies
• Retinal Ganglion Cells (pathology)
• Tomography, Optical Coherence
• Visual Acuity (physiology)
• Visual Fields (physiology)
• Young Adult