Intraocular lens power calculation for cataract surgery after photorefractive keratectomy for high myopia
W. E. Weingaertner, J. Kampmeier, C. W. Spraul, G. K. Lang
Introduction: The number of patients undergoing cataract surgery after photorefractive keratectomy (PRK) will increase. The altered corneal curvature makes the calculation of the power of the intraocular lens (IOL) difficult, especially in patients with high myopia and unknown keratometric values (K-values) before PRK.
Methods: Two patients, who had PRK for high myopia done elsewhere, underwent extracapsular cataract extraction (phacoemulsification) with posterior chamber lens implantation. Because of missing data of pre-PRK K-values, the intraocular lens calculation (SRK-II) was performed with the k-values reduced by 25%.
Results: The age of the patients was 57 and 46 years. PRK was performed 6 and 4 years ago. The refraction pre-PRK according to the PRK-surgeon was 16.0 dpt and 24. 5dpt (spherical equivalent). The refraction post-PRK was 5 dpt and 8.5 dpt (spherical equivalent). The postoperative refraction after IOL- implantation was +1.75 dpt and +1.5 dpt (spherical equivalent). The difference to the calculated refraction was 1.0 dpt and 2.52 dpt.
Conclusion: Intraocular lens power calculation in patients after photorefractive surgery is even more difficult in patients with high myopia and missing K-values before PRK. Standard calculation approaches are not efficient in these cases and have to be used modified. Great experience in calculation and high surgical skills are necessary. Nevertheless patients should be informed about the possibility of refractive surprises.
Department of Ophthalmology, University of Ulm, Prittwitzstraße 43, Germany 89075 Ulm