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Background
Recent studies have demonstrated that glaucoma progression had great relationship with corneal biomechanical properties.However, there are not enough studies about corneal biomechanical properties in different types of glaucoma.
Objective
This study was to evaluate the corneal biomechanical properties in chronic primary angle-closure glaucoma (CPACG) and primary open angle glaucoma (POAG).
Methods
Prospective observational study was adopted.Sixty-eight cases (68 eyes) with CPACG and 69 POAG patients (69 eyes) from Zhongshan Ophthalmic Center were investigated by a novel technique named Corvis-ST which can measure corneal deformation.The Cronbach’s α coefficient and intraclass correlation coefficient (ICC) were used to evaluate the repeatability of the parameters from Corvis-ST.The differences of corneal biomechanical properties between POAG and CPACG were evaluated by independent-samples t test.Multiple regression analysis was used to assess the association between parameters of deformation response and clinical factors.This study protocol was approved by Ethic Committee of Zhongshan Ophthalmic Center and complied with Helsinki Declaration.Written informed consent was obtained from each patient prior to any medical examination.
Results
There were no statistic differences about age, sex and intraocular pressure (IOP) between CPACG and POAG patients (all at P>0.05). However, differences existed in the number of anti-glaucoma medications (t=-2.388, P=0.020). Measurements of central corneal thickness (CCT), deformation amplitude (DA), and peak distance (PD) demonstrated excellent repeatability (ICC≥0.8). There were no statistic differences about CCT, first applanation time/length/velocity (A1T, A1L, A1V), second applanation time/length/velocity (A2T, A2L, A2V), DA between CPACG and POAG patients (all at P>0.05). The highest concavity time was shorter (t=2.920, P=0.005), PD was bigger (t=-2.453, P=0.017), and central curvature radius (CCR) was smaller (t=1.997, P=0.050) in POAG than those in the CPACG patients.DA, A1V, A2T and PD were negatively associated with IOP (r=-0.709, -0.531, -0.645, -0.554; all at P<0.001). However, A1T and A2V were positively associated with IOP (r=0.744, 0.546; both at P<0.001). And CCR was positively associated with CCT (r=0.181, P=0.039).
Conclusions
It is useable to evaluate corneal biomechanical properties of glaucoma by Corvis ST.Under the same level of IOP, the corneal concavity of POAG is easier than that of CPACG, which indicates that cornea in POAG patients is more deformable.