Visual Outcome After Femtosecond Laser Small-Incision Lenticule Extraction Versus Conventional LASIK
This study aims at assessment of visual outcome after femtosecond laser small incision lenticule extraction (SMILE) and compare it with conventional laser in situ keratomileusis (LASIK) for low and moderate myopia as regards the predictability, efficacy, safety, contrast sensitivity, and high-order aberrations outcome.
This is a prospective, comparative, non-randomized interventional study done on 40 eyes having myopia with or without astigmatism that were divided into 2 equal groups; first group had conventional LASIK and the second group had femtosecond laser small-incision lenticule extraction (SMILE). The myopia ranged between -2.75 and -8.0 D and astigmatism up to -3.0 D with age more than 18 years and pachymetry more than 490 microns. After the usual full ophthalmological assessment of 40 eyes for 20 patients asking for refractive surgery, ultrasonic pachymetry, topography, and Pentacam, scotopic contrast sensitivity curve was done before surgery, (WASCA) was done to measure lower and high-order aberrations (coma, fourth order spherical aberrations and secondary astigmatism), informed consent for all patients.
One and 3-month follow-up were done for 40 eyes of 20 patients aged between 19 and 51 years, regarding the visual outcome: predictability, safety, and efficacy showed no statistically significant difference in both groups. On comparing HOA, 1-month postoperatively: there was a statistically significant difference in the induced HOA RMS (p<0.001*), and induced secondary astigmatism (p=0.010*) were higher in the first group. After 3 months only the induced secondary astigmatism was statistically significant (p=0.0010) but not the HOA RMS, induced coma RMS or induced spherical aberrations. Contrast sensitivity 1 and 3-month postoperative comparison between both groups revealed a statistically significant difference in the LASIK group more than the SMILE group in (cpd 6, 12, and 18) (p=0.00*, p=0.032*, p=0.000*) but not in cpd3.
Preoperative contrast sensitivity scores decreased significantly in 1 and 3 months postoperatively persisted at all spatial frequencies in LASIK while in SMILE significant decrease in cpd3 and cpd12 and insignificant decrease in cpd6 and cpd18. LASIK induces more secondary astigmatism, Coma but SMILE induces more negative spherical aberrations and HOA RMS in postoperatively one month and less at three months. No difference between LASIK and SMILE in the quality, clarity, and night vision.