Posters

Determining cone location and cone size in corneal keratoconus patients with an inversed Finite Element Model – preliminary results

Poster Details

First Author: M.Vandevenne THE NETHERLANDS

Co Author(s):    M. Vandevenne   A. Boonstra   T. Berendschot   J. Rozema   A. Sinha Roy   R. Nuijts     

Abstract Details

Purpose:

To evaluate an inverse Finite Element Model (FEM) which uses tomography and biomechanical modelling to detect cone location and cone size in keratoconus patients, and to compare it with existing methods.

Setting:

University Eye Clinic Maastricht, Maastricht University Medical Center, the The Netherlands. In collaboration with Narayana Nethralaya Foundation, Bangalore, India and the Department of Ophthalmology, Antwerp University Hospital (UZA), Edegem, Belgium. A retrospective cohort study.

Methods:

The inverse FEM uses corneal tomography and biomechanical modelling to provide an estimate of the degeneration zone. The generation of a degeneration map takes up to 72 hours. To determine cone location we took the center of the degeneration zone from the degeneration maps, the maximal posterior elevation of the elevation map and the minimal corneal thickness of the pachymetry map. To measure cone size we calculated the mean diameter of the degeneration zone. In the posterior elevation map we measured the shortest distance between the maximum elevation and the cross-section between the best fit sphere and posterior elevation map.

Results:

Four eyes from 4 patients with keratoconus were included and 2 measuring moments of each patient were analyzed. Mean age (±SD) was 26±8years. A general linear model repeated analysis revealed significant differences in the cone locations between the different methods (p-value = 0.032). We found only a modest correlation of r=0.39 (p=0.34) between the diameter of the cone from the posterior elevation map and from the degeneration map.

Conclusions:

According to the literature, corneal biomechanical properties are essential in the onset of keratoconus. Measuring these properties would allow identification of cone location and size of corneal degeneration. This study shows, based upon limited evidence, that the methods to determine cone location and size are not in agreement with each other. The new method showed significant differences within the patients compared to the posterior elevation and pachymetry map. If these methods would be used for planning customized crosslinking procedures the results would differ significantly. Based upon these preliminary results it is clear that further research is necessary.

Financial Disclosure:

has significant investment interest in a company producing, developing or supplying product or procedure presented