Refractive surgery: Is the new small-incision lenticule extraction (SMILE) technique equal to or better than the standard flap-and-ablation (FS-LASIK) technique for treating high-degree myopia?

Field:
Ophthalmology
Introduction:
Corneal laser surgery for myopia (nearsightedness) is one of the most performed surgical procedures today. FS-LASIK has been the dominating surgical technique for almost two decades, but a shift to the new less invasive SMILE technique might be underway. However the literature on SMILE is sparse, especially for high-degree myopia (six or more dioptres (D)).
We hypothesize that the accuracy, efficacy, stability and safety after SMILE is equal to or better than FS-LASIK up to three months post-operatively for high-degree myopia.
Methods:
Retrospective study of 1214 eyes treated with SMILE or FS-LASIK for high-degree myopia from 2011-2013 at the Department of Ophthalmology, Odense University Hospital, Denmark. Inclusion criteria: Best spectacle-corrected visual acuity (BSCVA) of 20/25 or better on Snellen chart, and no other ocular condition than high-degree myopia with or without astigmatism of maximum 3 D.
Results:
In total 799 eyes completed the three months follow-up examination, of which 545 eyes were treated with SMILE (mean pre-operative refraction -7.63±1.37 D, range: -6 to -14.75) and 254 with FS-LASIK (mean pre-operative refraction -7.94±1.72 D, range: -6 to -16.50)
Accuracy: After three months 80% of SMILE eyes and 71% of FS-LASIK (P=0.38) were within ±0.5 D of attempted post-operative refraction, whilst 96% of SMILE and 90% of FS-LASIK (P=0.54) were within ±1.0.
Efficacy: In 180 eyes the attempted post-operative refraction was 0 D. Of these, 69% of SMILE and 83% of FS-LASIK (P=0.55) had an uncorrected visual acuity of 20/25 or better one day post-operative. After three months, the results were 95% for SMILE and 81% for FS-LASIK (P=0.73).
Stability: In total 39% of SMILE and 51% of FS-LASIK (P=0.07) changed ≥0.5 D in refraction from one day to three months post-operatively.
Safety: One SMILE eye (0.2%) and no FS-LASIK eyes had lost two or more lines of BSCVA after three months.

Conclusion:
This study is the most extensive of its kind, and our results indicate that the accuracy, efficiency, stability and safety of SMILE is equal to or better than FS-LASIK for high-degree myopia up to 3 months post-operatively.
Keywords:
Refractive surgery, SMILE, FS-LASIK, high-degree myopia