Effect of Biomechanical Properties on Myopia: a Study of New Corneal Biomechanical Parameters
Abstract Background: To investigate corneal stress-strain index (SSI), a marker for material stiffness and corneal biomechanical parameters in myopic eyes.Methods: A total of 1056 myopic patients were included in this study. Corvis ST was used to measure SSI. Corneal biomechanics was evaluated using the first and second applanation time (A1-time and A2-time), maximum deflection amplitude (DefAmax), deflection area(HCDefArea)and peak distance at highest concavity (HC-time, HC-DefA, and HC-PD), integrated radius (IR) whole eye movement (WEM), stiffness parameter (SP), biomechanically corrected intraocular pressure (BIOP), and Corvis Biomechanical Index (CBI). Scheimpflug tomography was used to obtain mean keratometery (Km) and central corneal thickness (CCT). All participants were divided into two groups according spherical equivalent (SE) (low myopia: SE≤3.00D and high myopia: SE ≥ 6.00D).Results: The mean SSI value was 0.854±0.004. The SSI has positive correlation with A1-time((r=0.272), HC-time (r=0.218), WEM(r=0.288),SP(r=0.316),CBI(r=0.199),CCT (r=0.125), BIOP(r=0.230)and SE (r=0.313)(all p values<0.01) . The SSI had a negative correlation with HCDefA (r=-0.721), HCDefArea (r=-0.665),HC-PD(r=-0.597),IR (r=-0.555), DefAmax (r=-0.564)and Km (r=-0.103) (all p values<0.01).There were significant differences in SSI (t=8.960, p<0.01) and IR(t=-3.509, p<0.01)between low myopia group and high myopia group.Conclusions: In different grades of myopia, the SSI values were lower in eyes with higher spherical equivalent. It indicates that the mechanical strength of the cornea may compromise in high myopia. The SSI was positively correlated with the spherical equivalent and It may provide a new way to study the mechanism of myopia.