Comparison of corneal biomechanics among primary open-angle glaucoma with normal tension or hypertension and controls.

ABSTRACT

BACKGROUND: Normal tension glaucoma (NTG) is a less pressure-dependent type of glaucoma with characteristic optic neuropathy. Recently, the biomechanical mechanism has been thought to account for glaucomatous optic neuropathy to some degree. We intended to compare dynamic corneal response parameters (DCRs) among patients with primary open-angle glaucoma with normal tension or hypertension and controls. The correlations between DCRs and known risk factors for glaucoma were also analyzed. METHODS: In this cross-sectional study, 49 NTG subjects, 45 hypertension glaucoma (HTG) subjects, and 50 control subjects were enrolled. We compared the differences in DCRs using corneal visualization Scheimpflug technology among the NTG, HTG, and control groups. We also analyzed the correlations between DCRs and known risk factors for glaucoma (eg, central corneal thickness [CCT], intraocular pressure [IOP], etc). RESULTS: The maximum inverse concave radius (NTG 0.18 [0.17, 0.20] mm-1; control 0.17 [0.16, 0.18] mm-1; P = 0.033), deformation amplitude ratio of 2 mm (DAR 2 mm, NTG 4.87 [4.33, 5.39]; control 4.37 [4.07, 4.88]; P < 0.001), and DAR 1 mm (NTG 1.62 [1.58, 1.65]; control 1.58 [1.54, 1.61]; P < 0.001) were significantly higher in NTG than in the controls. The integrated radius (IR, NTG 8.40 ±â€Š1.07 mm-1; HTG 7.64 ±â€Š1.31 mm-1; P = 0.026) and DAR 2 mm (NTG 4.87 [4.33, 5.39]; HTG 4.44 [4.12, 5.02]; P < 0.007) were significantly higher, whereas the stiffness parameter at the first applanation (SP-A1, NTG 91.23 [77.45, 107.45]; HTG 102.36 [85.77, 125.12]; P = 0.007) was lower in NTG than in HTG. There were no significant differences in the DCRs between HTG and control groups (P > 0.05). In the univariate and multivariate analyses, some of the DCRs, such as IR, were negatively correlated with CCT and IOP, whereas SP-A1 was positively correlated with CCT and IOP. CONCLUSIONS: The cornea was more deformable in NTG than in HTG or controls. There were no significant differences in corneal deformability between HTG and controls. The cornea was more deformable with the thinner cornea and lower IOP.