Structural differences have been reported between primary open angle glaucoma (POAG) and normal tension glaucoma (NTG), and biomechanical differences between POAG and NTG may account for why NTG patients are more vulnerable to lower intraocular pressure (IOP). This study compared the biomechanical properties of POAG and NTG patients using the Corvis scheimpflug technology (ST) non-contact Scheimpflug-based tonometer, and determined the factors associated with these properties.In this retrospective cross-sectional study, 46 eyes with POAG, 54 eyes with NTG, and 61 control eyes were included. A non-contact Scheimpflug-based tonometer was used to examine and compare the corneal biomechanical responses in the POAG, NTG, and normal groups. We used univariate and multivariate regression analyses to determine the factors associated with the deformation amplitude in each group.Baseline characteristics, including age, IOP, spherical equivalent, keratometry, axial length, and central corneal thickness, were similar among the 3 groups. Severity of glaucoma, as measured by mean deviation, was similar between POAG and NTG groups. Applanation 1 velocity and deformation amplitude were significantly smaller in POAG (0.13 ± 0.02 and 1.06 ± 0.14, respectively) than NTG (0.14 ± 0.01 and 1.13 ± 0.11, respectively) and normal groups (0.14 ± 0.02 and 1.13 ± 0.10, respectively). Radius of curvature was significantly larger in the POAG group compared to the normal group. In normal controls, IOP and keratometry were significant factors related to deformation amplitude. In POAG eyes, IOP was a statistically significant predictor of deformation amplitude. In NTG eyes, however, IOP , keratometry, and axial length were statistically significant predictors of deformation amplitude.POAG eyes showed less deformable corneas compared to NTG and normal controls. IOP was significantly correlated with deformation amplitude in all groups. However, axial length was positively correlated with deformation amplitude only in NTG eyes. Characterization of the differences in biomechanical properties between POAG and NTG may contribute to a better understanding of the underlying pathophysiologies associated with these diseases.
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