Posters

3D simulation of intrastromal corneal ring implant for keratoconus stabilization

Poster Details

First Author: J.Flecha SPAIN

Co Author(s):    M. Ariza-Gracia   B. Calvo Calzada   M. del Buey              

Abstract Details

Purpose:

Intrastromal Corneal Ring Segments (ICRS) are used in clinical practice to stabilize the progression of the non-inflammatory ectasia disease known as keratoconus (KTC). Usually, there are some uncertainties in the location of the ICRS during the surgery. Not only that, but the foreseen effects of the surgery are mainly based on statistical studies or surgeon experience. The present study aims to improve the comprehension of the effects of the ICRS insertion by means of a 3D in-silico model. After the simulation of the surgery, corneal optical features were obtained by means of ray-tracing.

Setting:

Applied Mechanics and Bioengineering (AMB), Aragón Institute of Engineering Research (I3A). University of Zaragoza, Zaragoza, Spain; ESKAS fellowship, ISTB, University of Bern, Switzerland; Department of Mechanical Engineering Energetics and Materials, Public University of Navarra, Pamplona, Spain;Bioengineering, Biomaterials and Nanomedicine Online Biomedical Research Center (CIBER-BBN), Zaragoza, Spain

Methods:

3D surgery simulation ICRS tool is resumed in 3 main steps: the generation of the 3D model eye, the numerical simulation of surgery, and the impact of the ICRS in the corneal optics. First, a Navarro’s 3D schematic eye model is built, accounting for the anisotropic behaviour of the cornea: two orthogonal set of collagen fibres were included. Second, a design of experiments is designed to analyse the set of most meaningful parameters: cross-section of the ring, insertion at different optical zones, and depth of insertion. Third, the wavefront of the optical system was computed by means of ray-tracing.

Results:

After the insertion of the ICRS, the corneal surface shifted backwards along the optical axis, flattening the center of the cornea. Hence, astigmatism was induced in all the cases. Bigger cross-section of the ICRS are prone to induce a higher astigmatism. In this vein, moving the ICRS away from the corneal center (increasing the optical zone) increased the spherical power of the wavefront. Not only that but 0.5 mm cross-section ICRS, generated a greatly distorted corneal surface that even inverted the trend of the astigmatic Zernike coefficients (Z4 – Z6 and Z12-Z14).

Conclusions:

ICRS have a great impact in vision, therefore it is essential to give a proper pre-surgical assessment and surgical planning. Since all the rings induced astigmatism it is necessary to define and strategy for its implantation, trying to minimize the residual astigmatism. Not only that, ICRS effectively absorbed stresses due to their high stiffness, acting as a contention and stabilization element. Then, further efforts must focus in adapting the study to patient-specific geometries, including different cross-sectional geometries, and studying the impact of the ICRS in the evolution of ectatic diseases.

Financial Disclosure:

NONE