Determination of Corneal Biomechanical Behavior in-vivo for Healthy Eyes Using CorVis ST Tonometry: Stress-Strain Index

Abstract

Purpose: This study aims to introduce and clinically validate a new algorithm that can determine the biomechanical properties of the human cornea in vivo . Methods: A parametric study was conducted involving representative finite element models of human ocular globes with wide ranges of geometries and material biomechanical behavior. The models were subjected to different levels of intraocular pressure (IOP) and the action of external air puff produced by a non-contact tonometer. Predictions of dynamic corneal response under air pressure were analyzed to develop an algorithm that can predict the cornea's material behavior. The algorithm was assessed using clinical data obtained from 480 healthy participants where its predictions of material behavior were tested against variations in central corneal thickness (CCT), IOP and age, and compared against those obtained in earlier studies on ex-vivo human ocular tissue. Results: The algorithm produced a material stiffness parameter (Stress-Strain Index or SSI) that showed no significant correlation with both CCT ( p > 0.05) and IOP ( p > 0.05), but was significantly correlated with age ( p < 0.01). The stiffness estimates and their variation with age were also significantly correlated ( p < 0.01) with stiffness estimates obtained earlier in studies on ex-vivo human tissue. Conclusions: The study introduced and validated a new method for estimating the in vivo biomechanical behavior of healthy corneal tissue. The method can aid optimization of procedures that interfere mechanically with the cornea such as refractive surgeries and introduction of corneal implants.

Age Distribution and Associated Factors of Cornea Biochemical Parameter Stress-Strain Index in Chinese Healthy Population

“…It was shown as an ideal method to estimate the mechanical properties of corneal tissue material. The distribution of SSI in Italian and Brazilian populations has been reported by previous studies and SSI was found to be signi cantly affected by age 8 . Chua observed that a lower corneal hysteresis (CH) in Chinese than Indians, suggesting that corneal biomechanics may be varies among different populations 11 .…”

“…Besides IOP, previous studies have shown that, parameters of corneal biomechanics in vivo were mostly affected by bIOP such as de ection area at the highest concavity and de ection amplitude (HC DefArea and HC DefA), SP -A1 38 CH and CRF 39 . However, SSI based on nite element (FE) numerical modeling simulating the effects of Corvis ST air puff and bIOP to predict of corneal behavior and excluded the in uence of bIOP, indicating that this is an ideal method for in vivo measurement of corneal tissue material stiffness 8 .…”

“…No signi cant effect was found in gender, ACV, corneal thickness, and bIOP.In our study, a nonlinear relationship was found between age and SSI, showing that SSI increased with age signi cantly after age of 35. Age has been shown to be an important factor affecting corneal biomechanical in previous study8 . Wang found a positive correlation between age and second…”

“…However, since cornea is consist of a viscoelastic material, and its stress-strain behavior of biological tissue is nonlinear 6,7 , the cornea shows the biomechanical properties of changes while under different intraocular pressure load. It is always a di cult problem to evaluate corneal biomechanics without the in uence of intraocular pressure in vivo [8][9][10] .…”

Künstliche Intelligenz zur Entwicklung von Screening-Parametern im Bereich der kornealen Biomechanik

“…Auch Finite-Elemente-Simulationen wurden durchgeführt, um den Zusammenhang zwischen Augeninnendruck und kornealer Biomechanik zu analysieren [6]. Diese Grundlagenforschung führte zur Entwicklung neuer biomechanischer Parameter, die direkt mit der Hornhautsteifigkeit [7] sowie dem Spannungs-Dehnungs-Verhalten der Hornhaut [8] zusammenhängen. Diese Parameter zeigten alle signifikante Unterschiede zwischen gesunden Augen und Augen mit Keratokonus [9].…”