Posters

Strain maps of topographically stiffened corneas derived by speckle shearing interferometry

Poster Details

First Author: A. Wilson UNITED KINGDOM

Co Author(s):    J. Marshall   J. Tyrer   A. Patemore   J. Jones           

Abstract Details

Purpose:

By using corneal cross-linking and other devices to increase the stiffness of specific regions of the cornea it has been possible to manipulate the shape of the cornea and design specific treatment plans for patients based upon their current refractive errors and topographies. Measurement of these biomechanical changes is fundamental to the development and success of such treatments. This paper details a lateral shearing interferometry technique capable of providing full field data on the dynamic mechanical response of the cornea to loading and demonstrates its ability to measure the biomechanical changes that occur as a results of cross-linking.

Setting:

Experiments were conducted at Loughborough University, Leicestershire, UK and UCL Institute of Ophthalmology, London, UK

Methods:

Porcine corneas were topographically stiffened using either applications of tissue glue or cross-linked using Riboflavin and UVA (10minute riboflavin soak, 2 x 5 minutes continuous at 5mW/cm2) in specific topographic locations. Experimental areas were removed as cornea-sclera buttons and positioned in an artificial anterior chamber under an initial hydrostatic pressure of 20mmHg. The dynamic response of the corneas to changes in hydrostatic pressure, comparable to those experienced physiologically during the cardiac cycle, were measured using a custom built out-of-plane lateral shearing interferometer in real time.

Results:

Strain maps obtained provided high resolution, full field data detailing how the corneal surface deformed during loading. The results successfully demonstrated the changes that occurred in the strain distribution of topographically cross-linked corneas due to changes in the biomechanical properties of specific regions when compared to untreated controls.

Conclusions:

Crosslinking in specific regions, potentially suitable for eliminating astigmatic errors, results in changes to corneal strain distribution under loading and this can be measured using lateral shearing interferometry.

Financial Disclosure:

One or more of the authors is employed by a forNONEprofit company with an interest in the subject of the presentation, One or more of the authors receives consulting fees, retainer, or contract payments from a company producing, developing or supplying the product or procedure presented