New predictive model of corneal biomechanics for myopic paediatric population using corneal tomography

Session Details

Session Title: Corneal Biomechanics

Session Date/Time: Monday 09/10/2017 | 08:00-10:30

Paper Time: 08:43

Venue: Room 2.1

First Author: : H.Matalia INDIA

Co Author(s): :    J. Matalia   M. Francis   P. Gogri   P. Panmand   R. Shetty   A. Sinha Roy     

Abstract Details

Purpose:

The effect of myopia on corneal biomechanical properties is relatively unknown. Also, instruments to measure biomechanics of the cornea are neither widely available nor affordable to most of the ophthalmologists. The primary objective was to determine the change in corneal biomechanical properties in a large cohort of eyes with myopic refractive error and to develop a new predictive model of corneal biomechanics for myopic pediatric population using corneal tomography parameters.

Setting:

Narayana Nethralaya, Bangalore, India

Methods:

733-eyes of children between 6-18 years, who visited pediatric ophthalmology clinic and co-operated for the examination, were included in the study. All eyes also underwent corneal tomography (Pentacam) and biomechanical assessment with air-puff applanation (Corvis-ST). Independent waveform analyses of the corneal deformation, recorded by Corvis-ST, was performed to derive corneal and extra-ocular tissue stiffness. Stiffness was an aggregate representation of corneal elastic modulus, intraocular pressure (IOP) and central corneal thickness (CCT). Based on the cycloplegic refraction, eyes were sub-grouped into emmetropic, hyperopic, myopia I (≥0D to <-3D), myopia II (-3D to -6D) and myopia III (>-6D) for multivariate analyses.

Results:

Corneal stiffness was lower by 3.72%, 6.84% and 10.68% in myopia I, II and III eyes, respectively, relative to emmetropic eyes. Extra-ocular tissue stiffness increased by 11.15%, 22.60% and 28.5%, respectively, in the same groups. Multivariate regression yielded age, IOP, CCT, corneal astigmatism, anterior chamber depth and refractive error as significant predictors of corneal stiffness, with high coefficient of regression (r=0.87). Based on this, two novel equations were derived to estimate linear and non-linear biomechanical stiffness of the cornea. The intra-class correlation between the measured and estimated values of linear and non-linear corneal stiffness was 0.90 and 0.93 respectively.

Conclusions:

Corneal stiffness was significantly lower in myopic eyes. Since age, IOP and CCT were similar between the grades, this decrease in stiffness can be attributed to decrease in elastic modulus only. Thus, the first evidence of biomechanical weakness in myopic eyes, in terms of stiffness and modulus, was observed. Using the regression formulae, we can now estimate corneal stiffness simply by using corneal tomography values.

Financial Disclosure:

NONE