Effects Of Axial Length And Corneal Curvature On Corneal Biomechanics In Elderly Population

Objective The reasearch is aimed at appling Corvis ST to research the character of the corneal biomechanics for the elderly with different axial length and corneal curvature.To compare the changes in corneal biomechanics after phacoemulsification.Methods Collection in November 2015 to September 2014,aged 60-80 year old to accept cataract surgery preoperative crowd of 220 people(426 eyes).Corneal biomechanical parameters are measured by Corvis ST,and the biomechanical parameters are compared between different sexes,different axial lengths and different corneal curvatures.The single factor variance analysis and independent sample t-test are used to count and analyze the correlation among the parameters of biomechanics of the each group.Further Prospective cohort study,collection the patients undergoing phacoemulsification were longer–axial length(AL:>26mm)and normal–axial length groups(AL: 22-24mm).Corvis ST was used to measure the biomechanical parameters of the cornea before operation,in the first postoperative week,and in the first postoperative month.The differences in the parameters between the two groups before operation were analyzed using the independent-samples t test.One-way analysis of variance,the Bonferroni test and Pearson correlation analysis were used for analysis.Results 1.There is no statistical significance for the difference of the corneal biomechanical parameters between men and women of the elder.2.The average first applanation length and the average second applanation length among different corneal curvatures have a statistical significance.3.There is statistical significance for the difference of the second applanation velocity,deformation amplitude,central cornea thickness,intraocular pressure.4.There is linear positive correlation between the patent's axial length,and deformation amplitude,intraocular pressure(r=0.429,P<0.001;r=0.278,P<0.001),but there is linear negative correlation between the patient's axial length and central cornea thickness,the second applanation velocity(r=-0.291,P<0.001;r=-0.415,P<0.001).5.In the first postoperative week and in the first postoperative month after phacoemulsification,statistically significant differences were found between the two groups in the peak distance,central corneal thickness and intraocular pressure,as well as the second applanation time and deformation amplitude in the longer–axial length group.6.In the longer–axial length group,the changes in central corneal thickness,intraocular pressure,and deformation amplitude were positively correlated with the axial length in the first postoperative week(r = 0.493,P=0.003;r =0.575,P<0.001;r=0.587,P < 0.001),whereas in the normal–axial length group,the changes in related parameters did not show a positive correlation with the axial length(r = 0.125,P=0.482;r =-0.083,P=0.639;r =-0.129,P=0.468).Conclusion 1.The corneal curvature and ocular axial length may be the factor affecting the corneal biomechanical characteristics.The longer axial length,the thinner corneal thickness,the more easily the corneal is deformed,and with the increase of the axial length,intraocular pressure also increases.2.Phacoemulsification can change the corneal biomechanical properties.These changes are more likely to occur in patients with longer axial length.Even,the intraocular pressure in patients with long eye axis has a rising trend.