Discriminating Diseases Mimicking Normal-Tension Glaucoma (NTG) from NTG

Background/Objectives: The aim of this study was to identify the most reliable ocular exam and establish a threshold for deciding whether to perform neuroimaging in order to screen for diverse diseases other than normal-tension glaucoma (NTG). A retrospective, observational, comparative study was used. Methods: In total, 106 individuals with atypical features of NTG who underwent glaucoma assessments and contrast-enhanced MRI of the brain or orbit were included. The criteria for atypical NTG included the following: (1) unilateral normal-tension glaucoma, (2) visual field (VF) damage inconsistent with optic disc appearance, (3) fast VF progression, (4) worsening of visual acuity, (5) optic disc pallor, (6) scotoma restricted by a vertical line, and (7) central scotoma. Glaucoma evaluations included measurements of visual acuity, intraocular pressure, central corneal thickness, axial length, cup-disc ratio, retinal nerve fiber layer (RNFL) thickness, ganglion cell-inner plexiform layer (GCIPL) thickness, mean deviation (MD), and visual field index (VFI). Statistical analyses involved independent t-tests, receiver operating characteristic (ROC) curves, and area under the curve (AUC) in order to differentiate neuro-ophthalmological conditions from NTG, compare the diagnostic power of each factor, and determine the cut-off value. Results: Relatively fewer diagnoses of non-glaucomatous diseases were associated with unilateral NTG, the worsening of VA, and central scotoma. Factors such as rapid visual field progression, optic disc pallor, and scotoma restricted by a vertical line had a relatively higher diagnostic rate of non-glaucomatous diseases. There were significant differences in average RNFL and GCIPL thicknesses at the nasal quadrant between NTG and NTG-mimicking conditions. Only the GCIPL thickness at the nasal quadrant had reliable power for discriminating between neuro-ophthalmological disease and NTG. For the GCIPL thickness at the nasal quadrant, the AUC was 0.659, and the cut-off value was 65.75. Conclusions: When deciding whether to proceed with imaging, such as carrying out an MRI test, for NTG patients with atypical NTG characteristics, it would be advisable to consider the nasal sector cut-off value of GCIPL thickness.