Analysis of peripapillary retinal nerve fiber layer and inner macular layers by spectral-domain optical coherence tomography for detection of early glaucoma

AIM: To analyze the diagnostic capabilities of peripapillary retinal nerve fiber layer (pRNFL) thickness and segmented inner macular layer (IML) thickness measured by spectral-domain optical coherence tomography for detection of early glaucoma.METHODS: Fifty-three patients with primary open angle glaucoma (POAG), 60 patients with normal tension glaucoma (NTG) and 32 normal control subjects were enrolled. Thicknesses of pRNFL, total macular layers (TML), and the IML, including macular RNFL (mRNFL) and macular ganglion cell layer (mGCL) were assessed. The areas under the receiver operating characteristic curves (AROC) were calculated to compare the diagnostic power of different parameters.RESULTS: There were no differences in the parameters of pRNFL, TML, and IML between POAG and NTG groups. The thicknesses of superior and inferior mGCL showed significant correlation with mean deviation of visual field (R2=0.071, P=0.004; R2=0.08, P=0.002). The mGCL thickness significantly correlated with the pRNFL thickness in the superior and inferior quadrants (R2=0.156, P<0.001; R2=0.407, P<0.001). The thickness of the inferior-outer sector of macula had greater AROCs than those in the inferior-inner sector of macula. The AROCs for superior (0.894) and inferior (0.879) pRNFL thicknesses were similar with the AROCs for superior (0.839) and inferior mGCL (0.864) thicknesses. Sensitivities at 80% specificity for global pRNFL, inferior-outer mGCL and inferior-outer mRNFL thicknesses were 0.938, 0.867, and 0.725, respectively.CONCLUSION: The diagnostic capability of the mGCL thickness is comparable to that of the pRNFL thickness in patients with early glaucoma. The inferior-outer sector of IML has a better diagnostic capability than the inferior-inner sector of IML for detection of early glaucoma.