RESUMO
Objective To compare the differences of corneal biomechanics in different types of glaucoma and its related influence factors,and to investigate the change trends of cornea biomechanics after the operations.Methods In a prospective comparative case series,61 eyes of 61 acute primary angle-closure glaucoma (APACG)(remission or chronic phase)patients,94 eyes of 94 chronic primary angle-closure glaucoma (CPACG) patients,70 eyes of 70 primary open angle glaucoma (POAG) patients and 64 eyes of 64 age-related cataract (ARC) patients were recruited in Tianjin Eye Hospital from January to July,2017.Corneal biomechanical properties were measured by using Corvis ST.The differences of corneal biomechanics in different types of glaucoma and the change trends after surgeries were assessed;the association between parameters and the age,intraocular pressure after correction (IOPcc),central cornea thickness (CCT),axial length (AL),average corneal diopter (K) were assessed by multiple linear regression analysis.This study followed the Declaration of Helsinki.This study protocol was approved by Ethic Committee of Tianjin Eye Hospital (TJYYLL-2016-17).Written informed consent was obtained from each subject prior to any medical examination.Results Compared with the ARC group,the first applanation velocity (A1V)and second applanation time (A2T) were both smaller in preoperative CPACG,POAG groups (all at P＜0.05);compared with the ARC group and APACG group,second applanation velocity (A2V) was larger in preoperative CPACG,POAG groups,the differences were all statistically significant (all at P＜0.05).A1V,A2T,deformation amplitude (DA) and peak distance (PD) were negatively correlated with IOPcc (r =-0.494,-0.612,-0.652,-0.277;all at P＜0.05),A2V,first applanation time (A1T) and central curvature radius (CCR) were positively correlated with IOPcc (r =0.508,0.960,0.249;all at P ＜ 0.05);first applanation length (A1 L) and second applanation length (A2L) were negatively correlated with K (r =-0.323,-0.227;both at P＜0.05);A 1 V,A2T and DA were positively correlated with K (r =0.214,0.256,0.242;all at P＜0.05).Compared with preoperative,the A1T and A2V were reduced,A1V,A2T and DA were increased in one month after surgery in CPACG group;the A1T and A2V were reduced,the A2T and DA were increased in one month after surgery in POAG group,and the differences were all statistically significant (all at P＜0.05).Compared with preoperative,there were no statistically significant differences between the parameters in one month after surgery in APACG group and ARC group (all at P ＞0.05).Conclusions CPACG and POAG have poorer ability of corneal deformation,which gradually returns to normal after surgery;because the intraocular pressure of APACG (remission or chronic stage) return to normal after transient elevated stage,the corneal biomechanics is basically similar to ARC,which has no difference between pre-and pos-operation.The parameters of corneal biomechanics are affected by IOPcc and K.
RESUMO
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 αt 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 (A1 T,A1 L,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.