Corneal Biomechanical Properties in Varying Severities of Myopia

Abstract

Purpose: To investigate corneal biomechanical response parameters in varying degrees of myopia and their correlation with corneal geometrical parameters and axial length.Methods: In this prospective cross-sectional study, 172 eyes of 172 subjects, the severity degree of myopia was categorized into mild, moderate, severe, and extreme myopia. Cycloplegic refraction, corneal tomography using Pentacam HR, corneal biomechanical assessment using Corvis ST and Ocular Response Analyser (ORA), and ocular biometry using IOLMaster 700 were performed for all subjects. A general linear model was used to compare biomechanical parameters in various degrees of myopia, while central corneal thickness (CCT) and biomechanically corrected intraocular pressure (bIOP) were considered as covariates. Multiple linear regression was used to investigate the relationship between corneal biomechanical parameters with spherical equivalent (SE), axial length (AXL), bIOP, mean keratometry (Mean KR), and CCT.Results: Corneal biomechanical parameters assessed by Corvis ST that showed significant differences among the groups were second applanation length (AL2, p = 0.035), highest concavity radius (HCR, p < 0.001), deformation amplitude (DA, p < 0.001), peak distance (PD, p = 0.022), integrated inverse radius (IR, p < 0.001) and DA ratio (DAR, p = 0.004), while there were no significant differences in the means of pressure-derived parameters of ORA between groups. Multiple regression analysis showed all parameters of Corvis ST have significant relationships with level of myopia (SE, AXL, Mean KR), except AL1 and AL2. Significant biomechanical parameters showed progressive reduction in corneal stiffness with increasing myopia (either with greater negative SE or greater AXL), independent of IOP and CCT. Also, corneal hysteresis (CH) or ability to dissipate energy from the ORA decreased with increasing level of myopia.Conclusions: Dynamic corneal response assessed by Corvis ST shows evidence of biomechanical changes consistent with decreasing stiffness with increasing levels of myopia in multiple parameters. The strongest correlations were with highest concavity parameters where the sclera influence is maximal.

High-Resolution Image Analysis Reveals a Decrease in Lens Thickness and Cone Density in a Cohort of Young Myopic Patients

“…Our findings are in agreement with previous studies that AL was negatively correlated with LT ( 19 , 20 ), positively correlated with ACD ( 20 ), and not correlated with CCT ( 21 , 22 ). Central corneal thickness, ACD, and LT are important components of AL.…”

Unraveling the mechanobiology of cornea: From bench side to the clinic

“…In a meta-analysis of corneal biomechanical properties of 11 related studies using an ocular response analyzer, we found that corneal elasticity decreased significantly in high myopia ( Wu et al, 2019 ). We further showed that corneal stiffness of over 1,000 patients with high myopia provided by Corvis ST also significantly reduced ( Han et al, 2020 ), which is further supported by the findings from other groups ( Zhang et al, 2018 ; Asano et al, 2019 ; Long et al, 2019 ; Kenia et al, 2020 ; Sedaghat et al, 2020 ; Tubtimthong et al, 2020 ). With an experimentally induced myopia model in chicks, the reduction of corneal elasticity and weakness of corneal biomechanics were related to development of myopia ( Kang et al, 2018 ).…”

Evaluation of corneal hysteresis after pars plana vitrectomy combined phacoemulsification and intraocular lens implantation

“…During this time, the rigidity and elasticity of the entire eye are reduced, and the eye structure is considered to be affected by external forces or ocular hypertension. CH was significantly lower in patients with high myopia than in healthy subjects 36 , 37 . In addition, the biomechanics of the cornea may reflect the biomechanics of the eye and predict the development of glaucoma 9 .…”