Impact of bio-mechanical indices on visual outcome up to five years after refractive lenticule extraction (ReLEx) SMILE

Session Details

Session Title: SMILE

Session Date/Time: Sunday 23/09/2018 | 16:30-18:00

Paper Time: 16:36

Venue: Room A3, Podium 2

First Author: : P.Hagen GERMANY

Co Author(s): :    D. Breyer   H. Kaymak   K. Klabe   T. Ax   F. Kretz   G. Auffarth     

Abstract Details

Purpose:

Former studies showed comparable visual recovery after ReLEx SMILE and Femto-LASIK. For LASIK, however, there is evidence that high PTA (Percent Tissue Altered) values might lead to regression of postoperative outcomes. Especially values above 40% are seen as a contributing factor to the development of late keratectasia. This retrospective analysis addresses the question whether there are similar surgical or corneal parameters that are correlated to regression after ReLEx SMILE. If this is the case, one would be able to identify SMILE-subgroups with increased risk for nonstable postoperative outcome.

Setting:

All ReLEx SMILE (VisuMax, CZM) surgeries were performed at the Breyer-Kaymak-Klabe Eyesurgery in Duesseldorf, Germany, which is part of the International Vision Correcton Research Center Network (IVCRC.net).

Methods:

We only included ReLEx SMILE eyes with existing pre- and postoperative (3 month and 1-5 years after surgery) data for CDVA, manifest refraction, and Scheimpflug tomography (Pentacam, Oculus). If available, data from deformation analysis (Corvis ST, Oculus) was also considered. Eyes with prior surgery were excluded. Parameters that were analyzed as potential regression-inducing factors were age, corneal shape/deformation parameters (Bad-D, CBT, TBI, etc.), as well as surgery parameters (relative lenticule thickness, PTA, etc.). Based on these parameters, a linear model was set up in order to explain the variation in postoperative regression of spherical equivalent, CDVA, keratometry readings, or pachymetry.

Results:

The rate of statistically significant (p<0.05) coefficients in the linear model was 6%, which is comparable to the significance level alpha itself. With respect to the above-mentioned regression observables, these coefficients did not display any systematic behavior. For instance, the relative lenticule thickness appeared to influence the regression of the spherical equivalent but not that of Kmax or Kmean. In addition all R^2 were below 0.1, meaning that any of the significant coefficients could only explain less than 10% of the observed total variation.

Conclusions:

From our linear model approach we conclude that all observed significances are purely statistical and that there is no consistent dependency between the postoperative regression after ReLEx SMILE and the considered shape, deformation, and surgery parameters. Thus, ReLEx SMILE yields equally stable long-term results over the full parameter range and no subgroup with increased risk for regression could be identified.

Financial Disclosure:

... receives consulting fees, retainer, or contract payments from a company producing, developing or supplying the product or procedure presented, ... travel has been funded, fully or partially, by a competing company, ... travel has been funded, fully or partially, by a company producing, developing or supplying the product or procedure presented, ... receives consulting fees, retainer, or contract payments from a competing company