Corneal Stiffness and Modulus of Normal-Tension Glaucoma in Chinese

Abstract

To assess and compare the corneal biomechanics of normal-tension glaucoma (NTG), high-tension glaucoma (HTG), and normal controls based on stiffness and modulus. The correlations among central corneal thickness (CCT), visual field, retinal nerve fiber layer (RNFL) thickness, and corneal biomechanics in glaucoma eyes were also evaluated. A prospective, cross-sectional, comparative study. This study included 334 eyes of 108 NTG patients, 113 HTG patients, and 113 control subjects at Zhongshan Ophthalmic Center, Sun Yat-Sen University. Corneal biomechanics were evaluated using a corneal indentation device (CID) and corneal visualization Scheimpflug technology (Corvis ST). Visual field and RNFL thickness were obtained using standard automated perimetry and spectral-domain optical coherence tomography. One-way analyses of variance with Bonferroni post hoc tests and a multivariable linear regression analysis with adjustment were conducted. Correlations among corneal biomechanical parameters, CCT, visual field, and RNFL thickness were analyzed. The corneal stiffness of the NTG patients (71.0 ± 10.9 N/m) was significantly lower than that of the HTG patients (77.3 ± 15.6 N/m; P=.001) and the CCT- and IOP-matched normal controls (75.6 ± 11.0 N/m; P=.023). The patients in the NTG group had lower corneal stiffness than those in the control group (β=-4.88, 95% CI -9.002, -0.758; P=.020) after adjusting for confounders. Stiffness was positively correlated with CCT in the NTG group (P=.028) but not in the HTG group (P= .509). There was no significant correlation (P > .05) between corneal biomechanics, visual field, or RNFL thickness. The corneas of NTG patients were softer than those of HTG patients and controls, as assessed by CID, which were associated with thinner CCT. These might suggest different ocular biomechanical properties in NTG and HTG.