Abstract
We evaluated changes in the pupillary light reflex (PLR) of ethambutol (EMB)-induced optic neuropathy and analyzed the correlations between PLR parameters and other structural changes in EMB-induced optic neuropathy. This retrospective, observational, case–control study involved thirty-two eyes of 17 patients with EMB-induced optic neuropathy (EON group), sixty eyes of 60 patients without EMB-induced optic neuropathy (non-EON group) while taking ethambutol, and forty-five eyes of 45 normal controls. PLR was measured by digital pupillometry. The clinical characteristics, optical coherence tomography measurements and PLR parameters including pupil diameter, constriction latency, constriction ratio/velocity, and dilation velocity were noted. The differences in PLR measurements were compared among the three groups. Correlations between PLR parameters and other structural parameters in EMB-induced optic neuropathy were evaluated. The pupillary constriction ratio, constriction and dilation velocities were significantly reduced in the EON group compared to the non-EON group and controls (all P < 0.05). In EMB-induced optic neuropathy, average outer macular ganglion cell layer (mGCL) thickness showed a significant correlation with the pupillary constriction ratio (ß = 4.14, P = 0.003) and maximal constriction velocity (ß = 1.08, P < 0.001). This study confirmed that pupillary constriction and dilation velocities were significantly decreased in patients with EMB-induced optic neuropathy, compared to normal controls. Digital pupillometry may be a useful tool in the evaluation of EMB-induced optic neuropathy.
Highlights
We evaluated changes in the pupillary light reflex (PLR) of ethambutol (EMB)-induced optic neuropathy and analyzed the correlations between PLR parameters and other structural changes in EMB-induced optic neuropathy
The mean best corrected visual acuity (BCVA) of the EON group was 1.07 logarithm of the minimum angle of resolution at initial presentation, which was significantly worse than the non-EON group and the control group
Pupillary constriction ratio, average and maximal constriction velocity, and average dilation velocity were significantly decreased in EMB-induced optic neuropathy compared to asymptomatic eyes of patients treated with EMB and normal controls
Summary
We evaluated changes in the pupillary light reflex (PLR) of ethambutol (EMB)-induced optic neuropathy and analyzed the correlations between PLR parameters and other structural changes in EMB-induced optic neuropathy. There has been a brief mention of pupil cycle prolongation in previous studies concerning patients on ethambutol therapy, but detailed analysis of the pupillary light reflex has not been documented[11,12] Recently, digital pupillometry enables objective quantification of PLR parameters[13,14]. This non-invasive and simple test has been proved to be effective in diagnosing other optic neuropathies and pupillary disorders[15,16]. We evaluated the correlations between PLR parameters and functional and structural measurements of the optic nerve
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