SMILE (small incision lenticule extraction) is a commonly used technique for correction of refractive error. It involves making a small incision in the peripheral cornea followed by cutting a lenticule in the stroma. Both the incision and lenticule are cut with a femtosecond laser. Since its introduction, SMILE has received both CE and FDA approval. There are several studies which demonstrate the clinical safety and efficacy of SMILE [1-4]. Further, SMILE may be associated with less dryness, pain and faster wound healing compared to LASIK (laser assisted in situ keratomileusis) and PRK (photorefractive keratectomy) [1-4].

References

1.      Kobashi H, Kamiya K, Shimizu K. Dry Eye After Small Incision Lenticule Extraction and Femtosecond Laser-Assisted LASIK: Meta-Analysis. Cornea. 2017 Jan;36(1):85-91.

2.      Liu YC, Teo EP, Lwin NC, Yam GH, Mehta JS. Early Corneal Wound Healing and Inflammatory Responses After SMILE: Comparison of the Effects of Different Refractive Corrections and Surgical Experiences. J Refract Surg. 2016 May 1;32(5):346-53.

3.      Zhang Y, Shen Q, Jia Y, Zhou D, Zhou J. Clinical Outcomes of SMILE and FS-LASIK Used to Treat Myopia: A Meta-analysis. J Refract Surg. 2016 Apr;32(4):256-65.

4.      Blum M, Täubig K, Gruhn C, Sekundo W, Kunert KS. Five-year results of Small Incision Lenticule Extraction (ReLEx SMILE). Br J Ophthalmol. 2016 Sep;100(9):1192-5.

We propose to conduct the following studies:

1)      In a small cohort of 20 patients with myopic refractive error, SMILE with the Schwind Laser (Titan) will be performed (n=40 eyes maximum or 20 patients). The efficacy parameter will be percentage of patients’ with manifest refractive error of ±0.25D of targeted refraction at 3 month follow-up. The preoperative refractive error would be limited to -3D spherical and 2D cylindrical error. If at least 80% efficacy is obtained, then the study will be expanded.

2)      The study then will be expanded to include 80 additional patients. SMILE with the Schwind laser (n=80 patients or 160 eyes maximum) will be performed. The main efficacy parameter will be percentage of patients’ with manifest refractive error of ±0.5D of targeted refraction at 3 month follow-up. The preoperative refractive error would be limited to -8D spherical and -5D cylindrical error.

Preoperative and postoperative examination will include:

 1)        Cycloplegic refraction

 2)        Visual Acuity – uncorrected and corrected distance visual acuity under mesopic conditions

 3)         Corneal tomography – Measured with Pentacam (OCULUS Optikegerate Gmbh, Germany)

 4)          Optical Coherence Tomography - Measured with RTVue (Optovue Inc, USA) to map epithelium thickness and curvature of the Bowman’s layer

 5)         Aberrometry and contrast sensitivity-  Measured with Visual Adaptive Optics simulator (Voptica Inc, Spain)·         

 6)        Corneal endothelial examination with specular microscopy

 7)          Dry eye assessment

If target refraction is not attained in any of the procedures, a retreatment will be done. Measurements will be performed at preoperative, week 1, month 1, month 3 and month 6. Study enrollment should take around 6 months.