Pupillary light reflex in ethambutol-induced optic neuropathy

Area of Science:

• Ophthalmology
• Neuroscience
• Pharmacology

Background:

• Ethambutol (EMB) is a first-line tuberculosis treatment.
• Optic neuropathy is a known adverse effect of EMB.
• Pupillary light reflex (PLR) abnormalities can indicate optic nerve dysfunction.

Purpose of the Study:

• To evaluate changes in PLR in ethambutol-induced optic neuropathy (EON).
• To analyze correlations between PLR parameters and structural changes in EON.
• To assess the utility of digital pupillometry in diagnosing EON.

Main Methods:

• Retrospective, observational, case-control study.
• Compared PLR parameters (pupil diameter, constriction latency, constriction ratio/velocity, dilation velocity) using digital pupillometry.
• Included patients with EON, patients taking ethambutol without EON, and normal controls.

Main Results:

• Patients with EON showed significantly reduced pupillary constriction ratio, constriction velocity, and dilation velocity compared to non-EON and control groups.
• Outer macular ganglion cell layer thickness correlated with pupillary constriction ratio and maximal constriction velocity in EON patients.
• Digital pupillometry identified significant PLR deficits in EON.

Conclusions:

• Pupillary constriction and dilation velocities are significantly decreased in EON.
• Digital pupillometry is a valuable tool for assessing EMB-induced optic neuropathy.
• PLR changes correlate with structural damage in EON, highlighting its diagnostic potential.