Posters

Current biomechanical argument for small incision lenticule extraction vs femtosecond laser-assisted in situ keratomileusis

Poster Details

First Author: B. Armstrong UNITED STATES

Co Author(s):                        

Abstract Details

Purpose:

This is a summary update of published work comparing biomechanical effects of small incision lenticule extraction (SMILE) to femtosecond laser-assisted in-situ keratomileusis (FS-LASIK). FS-LASIK creates a flap in the anterior corneal stroma, followed by ablation of the exposed stroma with an excimer laser. SMILE obviates the need for flap creation by use of a femtosecond laser to create and remove a stromal lenticule that corresponds to the desired refractive correction. It has been proposed that by preserving the integrity of the anterior corneal stroma, SMILE might minimize risk for postoperative weakness.

Setting:

Hospital based multi-specialty practice where both FS-LASIK and SMILE are being performed.

Methods:

Papers were identified by a comprehensive electronic search of relevant medical subject heading (MeSH) terms in PubMed. Identified articles were reviewed and rated for quality and relevance. Over 10 published articles were found to be relevant to this topic and analyzed. A multitude of methods have been used to compare the biomechanical properties in SMILE eyes versus FS-LASIK eyes. Methods include Ocular Response Analysis (ORA) incorporating corneal hysteresis (CH) and corneal resistance factor (CRF), Corvis ST analysis, computational/mathematical modeling, and shear modulus testing.

Results:

Overall corneal biomechanics are reduced after both FS-LASIK and SMILE. For ORA, the majority of studies showed statistically significant differences in CRF and CH values between FS-LASIK and SMILE. These values are significantly reduced in post FS-LASIK eyes compared to post SMILE eyes, especially in studies looking at higher refractive corrections. Computational and mathematical modeling as well shear modulus testing also acknowledge some biomechanical advantage for SMILE versus FS-LASIK. There appears to be no difference between the two procedures on Corvis-ST testing.

Conclusions:

SMILE seems to present less biomechanical risk compared to similar corrections with LASIK. By obviating the need for flap creation, the biomechanics of a SMILE cornea are more similar to those of an idealized cornea, leaving the strongest anterior corneal lamellae intact. As a result, corrections at greater stromal depths in SMILE may be possible with less relative risk of ectasia than a comparable LASIK correction.

Financial Disclosure:

NONE