Ray tracing simulations for small-aperture and toric IOLs in keratoconus eyes

Session Details

Session Title: Presented Poster Session: EDOF IOLs

Venue: Poster Village: Pod 1

First Author: : U.Oberheide GERMANY

Co Author(s): :    A. Grafov   H. Weigand   O. Kermani                 

Abstract Details

Purpose:

Keratoconus eyes eventually will develop age related cataract. Usually by then, the cornea has been treated or the process has stabilized anyway. Very often the optical properties of the conic corneas are significantly affected by irregular astigmatism. Up until now, the most we can do with IOL is to take care of the correction of sphere and cylinder. These eyes however, show clinically relevant amount of higher order aberrations, especially coma and trefoil, therefore only part of the irregular astigmatism is corrected. A new approach to the problem is the use of a small-aperture-IOL in these eyes.

Setting:

TH Köln (Cologne university of applied sciences, institute for optics and electronics) and Augenklinik am Neumarkt, Cologne (private eye hospital)

Methods:

Corneas of 10 keratoconus eyes where measured with a Scheimpflug-camera. The corneal tomography with elevation data of anterior and posterior surface is transferred into an optical design software to modify the Liou-Brennan-eye model with patient specific corneal data. Further adjustments to the standard eye model were done concerning axial length and anterior chamber depth. Raytracing in these patient models were performed for pseudophakic eyes with a toric intraocular lens and a spherical lens with a small aperture of 1.3 mm, as it is available on the market (Acufocus IC-8). Outcomes of cataract surgery are compared with these retrospective simulations.

Results:

After optimization of sphere and cylinder for best focal spot, the two types of lenses can be compared by through focus measurements, wavefront errors and point spread function. The small aperture simulations show better spot pattern in the through focus simulations as well as better point spread function compared to toriciol for cornea with high irregularities. These findings are confirmed by retrospective analysis of the surgical outcomes concerning shape of the point spread function, image simulation and relative amounts of wavefront errors.

Conclusions:

For patients with irregular corneas phacoemulsification and implantation of small-aperture-IOLs provide an alternative option for the correction of astigmatism compared to toric intraocular lenses. Since the number of cases is limited and keratoconic eyes show large interpatient variabilities no statistic values for the increase in strehl ratio or reduction in astigmatic power can be given and only case examples can be done.

Financial Disclosure:

None