Intraocular lens calculation in post-LASIK eyes using ray tracing with the data from a Placido disk-Scheimpflug tomographer

In a recent paper, Savini et al.1 compared several intraocular lens (IOL) calculation methods in eyes after laser in situ keratomileusis measured with the Galilei G6 device (Ziemer Ophthalmic Systems AG). Among the methods, they found the highest accuracy with Okulix ray-tracing software (Tedics Peric & Jöher GbR). Unfortunately, the authors say in the abstract that the paraxial, not the best-focus, calculation had the highest accuracy. In their tables, however, they use the correct (ie, the best-focus) value. The paraxial refractions of the Okulix are not to be used to show the refractive outcome. They are rather a simple measure of spherical aberration and a quality parameter for the implantation of aspheric IOLs. The higher the difference between paraxial and best-focus refraction, the higher the residual spherical aberration with the selected IOL model. In case of a zero difference, the pseudophakic eye has no spherical aberration.