Excimer Laser Treatment Of Highly Aberrated Corneas Including The Epithelial Thickness

In a prospective study, superficial excimer laser treatments were performed in highly aberrated corneas to improve the imaging quality. An epithelial map, which was created preoperatively by means of an anterior chamber OCT, is taken into account in the ablation profile. The main objective of this evaluation is to determine changes in aberrations up to the 6th order due to treatment with a laser system of the latest generation.

Medical University Vienna

In 20 highly aberrated corneas with an RMS HOA error (Root Mean Square Higher Order Aberration) of 1.0 - 4.0 μm, the aberrations of low and higher order up to the 6th order were recorded. The anterior chamber OCT MS-39® (Schwind) was used for the determination of the epithelial map. The ablation profile was created taking into account the middle epithelial thickness for the central 3 mm range. The treatments were carried out with the excimer laser Amaris 1050® (Schwind). After 6 months the changes in the aberrations were evaluated.

The postoperative refraction for the best corrected visual acuity was compared with the preoperative target refraction. Changes in the values for the aberrations up to the 6th order are shown graphically in diagrams. The simpler the aberration correction 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. The reductions in aberrations were statistically significant up to the 4th order.

With the excimer laser system used, aberrations can be reduced up to the 4th order. In particular, the rotationally symmetrical spherical aberration could be set very precisely to the target value.