Changes in corneal biomechanical properties before and after operation in different types of glaucoma

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 (A1L) and second applanation length (A2L) were negatively correlated with K (r=-0.323, -0.227; both at P<0.05); A1V, 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 post-operation.The parameters of corneal biomechanics are affected by IOPcc and K.