Official ESCRS | European Society of Cataract & Refractive Surgeons
Vienna 2018 Delegate Registration Programme Exhibition Virtual Exhibition Satellites 2018 Survey


escrs app advert

Ray tracing vs empirically optimised formulae for intraocular lens power calculation after SMILE

Search Title by author or title

Session Details

Session Title: Small Lenticule Extraction

Session Date/Time: Tuesday 25/09/2018 | 08:00-10:30

Paper Time: 09:09

Venue: Room A3, Podium 3

First Author: : N.Luft GERMANY

Co Author(s): :    J. Siedlecki   C. Wertheimer   T. Kreutzer   W. Mayer   S. Priglinger   M. Dirisamer     

Abstract Details


To compare ray tracing with empirically optimized formulae for intraocular lens (IOL) power calculation after small incision lenticule extraction (SMILE).


University Eye Hospital, Ludwig-Maximilians-University, Munich, Germany


This prospective cross-sectional study included patients that had undergone SMILE for myopia and/or myopic astigmatism at least 3 months previously. IOL power calculation was performed utilizing dedicated ray tracing software (Okulix, Version 8.81) based on corneal tomography scans (Pentacam HR; both: Oculus Optikgeräte GmbH, Wetzlar, Germany) aiming for plano residual refraction. The predicted postoperative residual refractive error of the IOL determined by ray tracing was compared with the residual refraction of the same IOL type (CT Asphina 404; Carl Zeiss Meditec AG) and IOL power as predicted by several empirically optimized IOL power calculation formulae.


A total of 48 eyes of 24 patients with a mean age of 36 ± 10 years were included. Preliminary results show that - compared with ray tracing - the Barrett True-K formula (with consideration of the surgically induced change in manifest refraction) resulted in the smallest absolute difference in predicted residual refraction (0.40±0.27 dpt; 61% within ±0.50dpt; 94% within ±1.0dpt). The Barrett True-K formula with no clinical history formula as well as the Haigis-L, Shammas, Masket, Modified Masket and Potvin-Hill formulae resulted in greater differences in predicted residual refraction after SMILE.


In the absence of data for empirical optimization of IOL power calculation after SMILE one must either rely on formulae optimized for eyes with different previous corneal refractive procedures (i.e. LASIK or PRK) or utilize a ray tracing approach. Amongst a variety of empirically optimized IOL power calculation formulae, the Barrett True-K formula (with clinical history) showed the closest agreement with ray tracing-based IOL power calculation after SMILE.

Financial Disclosure:


Back to previous