Langenbucher Achim, Szentmáry Nóra, Spira Corinna, Seitz Berthold, Eppig Timo
Experimentelle Ophthalmologie, Universität des Saarlandes, Kirrberger Straße 100, Gebäude 22, 66424 Homburg/Saar.
Klinik für Augenheilkunde, Universitätsklinikum des Saarlandes, Kirrberger Straße 100, Gebäude 22, 66424 Homburg/Saar; Klinik für Augenheilkunde, Semmelweis Universität, Mária utca 39, 1085 Budapest, Ungarn.
Z Med Phys. 2016 Jun;26(2):120-6. doi: 10.1016/j.zemedi.2015.02.003. Epub 2015 Mar 17.
Descemet stripping automated endothelial keratoplasty (DSAEK) is an established treatment option for pathologies of the corneal endothelium. It is typically accompanied with a hyperopic shift in refraction. The purpose of this work is to predict corneal geometry after DSAEK based on model data and to present a concept how to determine corneal power, e.g. for intraocular power calculation to prevent a refractive surprise with a subsequent cataract surgery.
Based on data of the Kooijman schematic model eye we simulated a microkeratome cut parallel to the corneal front surface for donor trephination to determine the radial thickness profile of the posterior corneal donor lamella. This donor lamella was tension-neutrally adapted to the back surface of the host and the profile of the cornea after DSAEK was derived and characterized by a quadric surface. Comparison with the curvature of the host without and with donor could resample hyperopic shift which was published in literature. A method was shown how to determine corneal power after DSAEK.
From the data of the Kooijman schematic model eye and the donor characteristics central / peripheral corneal thickness was increased by 150 / 250μm due to adaptation of the donor lamella. Geometry of corneal back surface showed a reduced radius of curvature (by about 0.9mm) and a change in conic constant (by about -0.13). Persistent clinically observed hyperopic shift correlates to the change in geometry of the cornea due to adaptation of the donor lamella, which reduces corneal power by 0.88 D.
DSAEK leads to a hyperopic shift in refraction, which can be explained by a change in corneal back surface geometry. In case of subsequent cataract surgery, the intraocular lens power should be calculated with consideration of both corneal surfaces rather than keratometry or corneal topography in order to minimize a systematic hyperopic shift due to misinterpretation of corneal power after DSAEK. In case of a Triple-DSAEK, a target refraction of -1.5 D should be chosen in order to safely prevent postoperative hyperopia.
