TRANSEPITHELIAL PRK IN HIGHLY ABERRATED CORNEAS CONSIDERING THE CENTRAL EPITHELIAL THICKNESS

In a prospective study, transepithelias PRKs were performed in highly aberrated corneas to reduce corneal irregularities. The epithelial thickness map, determined by an anterior chamber OCT, was included in the calculation of the ablation profile. The main objective of this study is to compare changes in aberrations before and after treatment.

Medical Univerity Vienna

Department of Ophthalmology and Optometrie

Transepithelial PRK was performed on 35 highly aberrated corneas with an RMS HOA (root mean square higher order aberration) error of 1.0 – 4.0 μm. The anterior chamber OCT MS-39® (Schwind) was used to determine the epithelial map. The ablation profile was created taking into account the mean epithelial thickness for the central 3 mm area. Low and high order aberrations up to the 6th order were evaluated before and 6 month after the treatment.

The postoperative refraction for the best corrected visual acuity showed good agreement with the predicted refraction requirement postoperatively. Changes in the values ​​for the aberrations up to the 6th order showed that the simpler the aberration correction is in terms of its three-dimensional shape, the better the result, this applies in particular to rotationally symmetrical corrections. Coma and Trefoil could be reduced by up to 40%, while spherical aberration was almost completely reduced according to the specification of 0.2 µm. The reduction in aberrations was statistically significant up to the 4th order.

Depending on the pre-existing aberrations, the excimer laser system used achieves a clinically significant reduction in aberrations up to the 4th order.