Influence of the flap on outcomes in corneal refractive surgery with femtosecond laser: SMILE vs. FLEx.

OBJECTIVE

To investigate the influence of creating a flap on the postoperative optical quality of the cornea in terms of predicted corneal curvature and Seidel aberrations after 2 modalities of femtosecond assisted corneal lenticule extraction laser for the correction of myopia and myopic astigmatism: The flapless procedure small incision lenticular extraction (SMILE) and the flap-based femtosecond lenticular extraction (FLEx).

METHODS

The study is a prospective consecutive non-randomised comparative interventional case series including 64 eyes with myopic or myopic astigmatism refractive errors. Patients were divided into 2 groups matched for age, sex and myopia. One group underwent SMILE treatment and the other underwent FLEx treatment. Seidel aberrations root-mean-square values were obtained with a 10mm aperture using the ATLAS 9000 topographer before surgery and 3 months after surgery. The relationship between the post-surgical corneal radius and the predicted sculpted radius were analysed in each group.

RESULTS

The mean percentage change in the curvature radius was -2.03% in the FLEx group and -1.77% in the SMILE group (P=.655). The higher correlation for the SMILE group demonstrates a better predictability after the surgery. As regards corneal aberrations, the FLEx treatment showed a greater increase of higher order aberrations than SMILE treatment (P=.04).

CONCLUSION

The mean refractive change in corneal curvature, which is indirectly related to the biomechanical response of the corneal surface after the lenticule cut and extraction, was similar after both treatments. However, the flap based FLEx procedure showed a greater degradation of the corneal optical quality in terms of induction of higher order aberrations.