gms | German Medical Science

Introduction: Laser assisted keratomileusis (Lasik) is currently the dominant form of corneal refractive surgery and has been incrementally optimized for more than 20 years. Small Incision Lenticule Extraction (SMILE) was introduced in 2008 and has also undergone many refinements. It has theoretical advantages: less induction of dry eye and better biomechanical stability. Is Lasik still the dominant procedure?

Methods: In order to reflect our current results, we evaluated the results at 1 month of 2 consecutive series of myopic eyes: 96 eyes with low myopia (SE>–3D), and 90 eyes with high myopia (SE<–7D). All flaps were created with the Ziemer Z6, and all ablative treatments were performed with the Schwind Amaris topo-guided software centered on the corneal vertex. We also reviwed the Lasik results with other recent platforms (Allegretto and VISx), and performed a critical review of the published litterature on SMILE.

Results: In the low myopia group uncorrected visual acuity (UCVA) of 20/20 or better was achieved by 96% of eyes on day 1, and 99% of eyes at 1 month. In the high myopia group UCVA of 20/20 or better was achieved by 69% of eyes on day 1, and 91% of eyes at 1 month. There were no cases of clinically significant dry eye. No eye lost 2 or more lines of best corrected acuity (BCVA). The efficacy of the other excimer platforms was similar with well over 90% 20/20 UCVA. Our review of SMILE shows that UCVA results have steadily improved over time, but have not achieved similar levels, that there is significantly more loss of 2 lines of BCVA (1.5 to 2.5%), and that vision recovers much more slowly, in some cases over several months. Compared to Lasik, there is less loss of corneal sensation after SMILE, but no clinically signficant differences in dry eye. Clinical biomechanical studies have so far not demonstrated a definite advantage of SMILE over Lasik.

Discussion: Several issues need to be resolved before SMILE can become the dominant procedure: better refractive results and safety, faster visual recovery, less inflammation (since unable to lift flap when it occurs), lack of eye-tracking, how to best re-treat. SMILE is an exciting technology which willl certainly evolve. Lasik is however still the gold standard.