Abstract:Objective: To investigate the structural injury patterns in retinal ganglion cell injury from ethambutol (EMB) treatment, and the value of Cirrus-HD OCT examination in the early diagnosis of toxic optic neuropathy. Methods: This was a retrospective case-control study. Sixty tuberculosis (TB) patients who took anti-TB drugs containing EMB from January 2018 to March 2019 were recruited. Among them, 6 patients (12 eyes) who were diagnosed with ethambutal-induced optic neuropathy (EON) were included in the EON group, another 43 patients (85 eyes) who had normal visual function after taking the medicine were included in the drug group. Forty-one patients (82 eyes) who matched the age and gender of the drug group were included in control group 1, and 13 patients (26 eyes) who matched the age and gender of the EON group were included in control group 2. The thickness of the retinal nerve fiber layer (RNFL) and the ganglion cell-inner plexiform layer (GCIPL) on Cirrus-HD OCT images were compared with those of healthy controls. Results: No significant changes in RNFL thickness were found in the drug group compared with control group 1. Meanwhile, the ganglion cell layer visibly decreased in the nasal-superior, nasal-inferior, inferior, temporal-superior and the superior sectors compared with control group 1 (t=-3.149, -2.880, -3.816, -3.697, -2.646, -2.231, -2.323, all P<0.05), except for the temporal inferior sector. The p-RNFL thickness of the EON group increased in the nasal and inferior sectors (t=2.452, 2.314, both P<0.05), while the ganglion cell layer thickness decreased in the nasal-superior, nasal-inferior, inferior, temporal-inferior, temporal-superior and the superior sectors compared with the healthy controls in group 2. The differences were significant (t=-2.809, -2.622, -2.806, -2.461, -2.887, -3.478, all P<0.05). Conclusions: CirrusHD OCT can accurately measure the thickness of the GCL layer, and enables more direct observance of damage to retinal ganglion cells. Combined with the measurement of p-RNFL and GCL thickness, it can assist in the early diagnosis of EON.
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