A clinical method for estimating the modulus of elasticity of the human cornea in vivo.

David C Pye,Sanjoy Bhattacharya

doi:10.1371/journal.pone.0224824

Abstract

BackgroundTo develop a method, using current clinical instrumentation, to estimate the Young’s modulus of the human cornea in vivo.MethodsCentral corneal curvature (CCC), central corneal thickness(CCT), intraocular pressure (IOP) was measured with the Goldmann tonometer (IOPG) and the Pascal Dynamic Corneal Tonometer(PDCT) in one eye of 100 normal young human subjects (21.07 ± 2.94 years) in vivo. The Orssengo and Pye algorithm was used to calculate the Young’s modulus of the corneas of these subjects.ResultsThe Young’s modulus(E) of the corneas of the subjects using the PDCT and IOPG results (Ecalc) was 0.25 ± 0.10MPa, and without the PDCT results (Eiopg) was 0.29 ± 0.06MPa. The difference in these results is due to the difference in tonometry results between the two instruments, as the mean PDCT result for the subjects was 16.89 ± 2.49mmHg and the IOPG result 15.06 ± 2.71mmHg. E was affected by the CCC of the subjects but more particularly by the CCT and IOP measurements. Corneal stiffness results are also presented.ConclusionTwo methods have been developed to estimate the Young’s modulus of the human cornea in vivo using current clinical instrumentation. One method (Ecalc) is applicable to the general corneal condition, and Eiopg to the normal cornea, and these results can be used to calculate corneal stiffness.

Highlights

There has been an increasing interest in the biomechanical behaviour of the eye[1], and especially of the cornea as demonstrated by Dupps and Roberts[2]
The Young’s modulus(E) of the corneas of the subjects using the PDCT and IOPG results (Ecalc) was 0.25 ± 0.10MPa, and without the PDCT results (Eiopg) was 0.29 ± 0.06MPa. The difference in these results is due to the difference in tonometry results between the two instruments, as the mean PDCT result for the subjects was 16.89 ± 2.49mmHg and the IOPG result 15.06 ± 2.71mmHg
E was affected by the Central corneal curvature (CCC) of the subjects but more by the CCT and intraocular pressure (IOP) measurements

Summary

Introduction

There has been an increasing interest in the biomechanical behaviour of the eye[1], and especially of the cornea as demonstrated by Dupps and Roberts[2]. One of the key values for the biomechanical behaviour of a tissue is a measurement of the way the tissue behaves when subjected to an applied load (or stress). This gives rise to a stress/ strain ratio called Young’s modulus, and this is a key value to be incorporated into engineering models of the cornea which include corneal topography, intraocular pressure and other characteristics of the eye to enable the behaviour of the tissue to be better understood

Methods

Results

Conclusion