Retinal ganglion cell-inner plexiform and nerve fiber layers in neuromyelitis optica

AIM： To determine the thickness of the retinal ganglion cell-inner plexiform layer（GCIPL） and the retinal nerve fiber layer（RNFL） in patients with neuromyelitis optica（NMO）.METHODS： We conducted a cross-sectional study that included 30 NMO patients with a total of 60 eyes. Based on the presence or absence of optic neuritis（ON）, subjects were divided into either the NMO-ON group（30 eyes） or the NMO-ON contra group（10 eyes）. A detailed ophthalmologic examination was performed for each group; subsequently, the GCIPL and the RNFL were measured using highdefinition optical coherence tomography（OCT）. RESULTS： In the NMO-ON group, the mean GCIPL thickness was 69.28±21.12 μm, the minimum GCIPL thickness was 66.02±10.02 μm, and the RNFL thickness were 109.33±11.23, 110.47±3.10, 64.92±12.71 and 71.21±50.22 μm in the superior, inferior, temporal and nasal quadrants, respectively. In the NMO-ON contra group, the mean GCIPL thickness was 85.12±17.09 μm, the minimum GCIPL thickness was 25.39±25.1 μm, and the RNFL thicknesses were 148.33±23.22, 126.36±23.45, 82.21±22.30 and 83.36±31.28 μm in the superior, inferior, temporal and nasal quadrants, respectively. In the control group, the mean GCIPL thickness was 86.98±22.37 μm, the minimum GCIPL thickness was 85.28±10.75 μm, and the RNFL thicknesses were 150.22±22.73, 154.79±60.23, 82.33±7.01 and 85.62±13.81 μm in the superior, inferior, temporal and nasal quadrants, respectively. The GCIPL and RNFL were thinner in the NMO-ON contra group than in the control group（P〈0.05）; additionally, the RNFL was thinner in the inferior quadrant in the NMO-ON group than in the control group（P〈0.05）. Significant correlations were observed between the GCIPL and RNFL thickness measurements as well as between thickness measurements and the two visual field parameters of mean deviation（MD） and corrected pattern standard deviation（PSD） in the NMO-ON group（P〈0.05）. CONCLUSION： The thickness of the GCIPL and RNFL, as measured using OCT, may indicate optic nerve damage in patients with NMO.

Macular thickness as a predictor of loss of visual sensitivity in ethambutol-induced optic neuropathy

Ethambutol is a common cause of drug-related optic neuropathy.Prediction of the onset of ethambutol-induced optic neuropathy and consequent drug withdrawal may be an effective method to stop visual loss.Previous studies have shown that structural injury to the optic nerve occurred earlier than the damage to visual function.Therefore,we decided to detect structural biomarkers marking visual field loss in early stage ethambutol-induced optic neuropathy.The thickness of peripapillary retinal nerve fiber layer,macular thickness and visual sensitivity loss would be observed in 11 ethambutol-induced optic neuropathy patients（22 eyes） using optical coherence tomography.Twenty-four healthy age-and sex-matched participants（48 eyes） were used as controls.Results demonstrated that the temporal peripapillary retinal nerve fiber layer thickness and average macular thickness were thinner in patients with ethambutol-induced optic neuropathy compared with healthy controls.The average macular thickness was strongly positively correlated with central visual sensitivity loss（r2=0.878,P=0.000）.These findings suggest that optical coherence tomography can be used to efficiently screen patients.Macular thickness loss could be a potential factor for predicting the onset of ethambutol-induced optic neuropathy.