Corneal Biomechanics In Diabetic Retinopathy

Research BasicsThe shape and curvature of the cornea are determined by its inherent biomechanical properties and external environment.In the past 10 years,the development of corneal biomechanics has received increasing attention.It is believed that the cornea,as a viscoelastic structure,can be affected by ocular and systemic conditions.Diabetes mellitus,as a systemic disease,often causes eye complications.At the same time,the incidence of diabetes is increasing year by year,and more and more diabetic eye diseases,such as diabetic retinopathy,diabetic optic neuropathy and other diseases are also increasing year by year.As a proliferative disease,diabetic retinopathy rarely occurs some other corneal diseases,such as keratoconus,high myopia,etc.,and patients with diabetic retinopathy often have higher intraocular pressure,thicker cornea and shorter axis length.And there is an increasing evidence that diabetes also affects corneal structure and biomechanics.These changes include increased glycosylation of proteoglycan and glycosaminoglycan,and accumulation of advanced glycosylation end products(AGEs).In addition,collagen fibrils and proteoglycan were highly cross-linked in the corneal stroma.The corneal microstructure changes may lead to changes in corneal biomechanics in diabetic patients,which may affect corneal refraction and intraocular pressure measurements.ORA is a device for measuring corneal biomechanical properties in vivo.It uses a dynamic bidirectional flattening technology to measure corneal biomechanical properties and to correct the effects of corneal biomechanical properties on IOP measurements,allowing accurate measurement of IOP.Exploring the changes of corneal biomechanical parameters and intraocular pressure is helpful to understand the effects of diabetes on corneal physiological structure and intraocular pressure in diabetic patients,so as to facilitate the early diagnosis and treatment of the disease.ObjectiveTo investigate the changes of corneal biomechanical parameters corneal hysteresis(CH)and corneal resistance factor(CRF)in patients with diabetic retinopathy,and to explore the effects of HbAlc,the degree of diabetic retinopathy,the duration of diabetes,central corneal thickness and intraocular pressure on CH and CRF.MethodsIn this study,87 patients(87 eyes)with diabetic retinopathy were enrolled in the Department of Ophthalmology,First Affiliated Hospital of Zhengzhou University from June 2020 to January 2021.The diabetic retinopathy group included 45 males and 42 females.The age of the patients in diabetes group ranged from 27 to 69 years,and the mean age was 54.16± 10.45 years.The control group included 31 healthy eye of non-diabetic patients with other eye diseases who received treatment in our department.The control group included 17 males and 14 females.The age of patients in the control group ranged from 26 to 71 years,and the mean age was 57.52±10.16 years.All patients were selected with the left eye.After routine ophthalmological examination corneal central thickness was measured by corneal topography,corneal biomechanical parameters were measured by ORA and axial length was measured by IOL Master.Fastening elbow venous blood was collected the next morning to detect HbAlc.IBM SPSS 21.0 statistical software was used to analyze all data.Differences between the two independent sample were compared using t test.Chi-square test was used to analyze the classified data.One way ANOVA was used to analyze difference among groups.LSD-t test was used to analyze difference between two groups.CH and CRF were corrected by covariance,and pairwise comparison was made by Bonferroni correction test.Pearson correlation analysis was used to analyze correlation between two groups of measurement data.Multiple linear regression was used to analyze the relationship between CH,CRF and the related influence factors.Result1.Compared with the control group,the DR group had higher CH,CRF,IOPcc,I OPg and CCT values,and the differences between DR group and the control group were statistically significant(P<0.05).2.After multiple linear regression analysis,it was showed that IOPcc and CCT were independent influencing factors for the corneal biomechanical characteristics of CH in DR patients,and age,IOPcc and CCT were independent influencing factors for corneal biomechanical characteristics of CRF in DR patients.While gender,axis,BMI,HbAlc,duration of diabetes,and degree of diabetic disease were not significantly correlated with CH and CRF(P>0.05).3.According to HbAlc,the DR group was divided into the HbA1c>7%group and the HbAlc<7%group.IOPcc and IOPg in HbAlc>7%group were higher than those in HbAlc<7%group,and the difference was statistically significant(P<0.05);There was no significant difference between CCT,CH,CRF,adjusted CH and adjusted CRF in HbAlc≥7%group and HbAlc<7%group(P>0.05)4.According to the degree of diabetic retinopathy,the diabetic group was divided into PDR group and NPDR group.There were no significant differences in CCT,CRF,CH,IOPcc,IOPg,adjusted CH and adjusted CRF between PDR group and NPDR group(P>0.05).5.According to the duration of diabetes,the diabetic group was divided into diabetic duration>10 years group and ≤ 10 years group.There was no significant difference in CRF,CH,IOPcc,IOPg,adjusted CH and adjusted CRF between diabetic duration>10 years group and diabetic duration≤10 years group(P>0.05).6.After Pearson correlation analysis,there was a moderate correlation between CH and CCT(P<0.01,r=0.45);There was a moderate correlation between CRF and CCT(P<0.01,r=0.46).CH and CRF increased by 0.02 mmHg when CCT increased by 1μm.7.After Pearson correlation analysis,there was a weak correlation between CH and IOPcc(P<0.01,r=0.33).The correlation between CRF and CCT was moderate(P<0.01,r=0.44).IOPcc per 1 mmHg increase,CH decreases 0.12 mmHg,and CRF increases 0.18 mmHg.Conclusion1.The corneal mechanical characteristics of patients with type 2 diabetic retinopathy were increased in CH and CRF,and CCT,IOPcc and age were independent influencing factors for CH or CRF.2.In patients with diabetic retinopathy,CCT and IOPcc increased,CH and CRF were positively correlated with CCT,CH was negatively correlated with IOPcc,and CRF was positively correlated with IOPcc.3.In the non-proliferative stage of diabetic retinopathy or when HbAlc<7%,CH and CRF increase,and then with the exacerbation of diabetic retinopathy and the increase of HbAlc,CCT or IOPcc increase significantly,and CH and CRF increase under the influence of multiple factors.