Small incision lenticule extraction (SMILE) techniques: patient selection and perspectives

Abstract

Refractive lenticule extraction is becoming the procedure of choice for the management of myopia and myopic astigmatism owing to its precision, biomechanical stability, and better ocular surface. It has similar safety, efficacy, and predictability as femtosecond laser-assisted in situ keratomileusis (FS-LASIK) and is associated with better patient satisfaction. The conventional technique of small incision lenticule extraction (SMILE) involves docking, femtosecond laser application, lenticule dissection from the surrounding stroma, and extraction. It has a steep learning curve compared to conventional flap-based corneal ablative procedures, and the surgical technique may be challenging especially for a novice surgeon. As SMILE is gaining worldwide acceptance among refractive surgeons, different modifications of the surgical technique have been described to ease the process of lenticule extraction and minimize complications. Good patient selection is essential to ensure optimal patient satisfaction, and novice surgeons should avoid cases with low myopia (thin refractive lenticules), difficult orbital anatomy, high astigmatism, or uncooperative, anxious patients to minimize complications. A comprehensive MEDLINE search was performed using “small incision lenticule extraction,” “SMILE,” and “refractive lenticule extraction” as keywords, and we herein review the patient selection for SMILE and various surgical techniques of SMILE with their pros and cons. With increasing surgeon experience, a standard technique is expected to evolve that may be performed in all types of cases with optimal outcomes and minimal adverse effects.

First Experience in Small Incision Lenticule Extraction with the Femto LDV Z8 and Lenticule Evaluation Using Scanning Electron Microscopy

“…Both the Femto LDV Z8 and VisuMax featured standard techniques of SMILE such as docking, femtosecond laser application, lenticule dissection, and extraction. [ 8 ] Nonetheless, there are still subtle differences between the two platforms. The centration of the target lenticule, for example, is based on high resolution OCT images in Femto LDV Z8, but is seen as real-time video in VisuMax; if the centration of the docking does not satisfy the surgeon, quantizable offsetting can be performed without releasing the suction via Femto LDV Z8, but not by VisuMax; Another difference is that two cap opening incisions were created by the Femto LDV Z8, but only one by VisuMax.…”

SMILE – Small Incision Lenticule Extraction

“…Dementsprechend sollten wenig erfahrene Operateurinnen und Operateure bei Vorliegen von erschwerten Bedingungen die Femto-LASIK der SMILE vorziehen. Dazu gehören [21]: ▪ sehr niedrige Myopie (dünner Lentikel), ▪ kleiner Weiß-zu-Weiß-Abstand, ▪ steile Keratometriewerte, ▪ tiefliegende Augen, ▪ enge Lidspalte, ▪ prominente Nase (jeweils Risikofaktoren für Saugverlust), ▪ hoher Astigmatismus (schwierige Zyklotorsionskontrolle), ▪ ausgeprägte präoperative Unruhe.…”

The effect of thin lenticule versus thick lenticule (a cut-off value of 55 micrometer) on the outcome of SMILE in low myopia

“…8 A paradigm shift has been marked by refractive lenticule extraction in the refractive surgery field from the well-known and practiced flap-based corneal ablative techniques to flapless extraction method of femtosecond laser-produced intrastromal lenticules. 9 The extraction of an intrastromal lenticule has been described by Sekundo et al following lifting a flap in 2008, and the procedure has been developed to the SMILE, a procedure in which a small 2-5-mm side cut incision is made through which the refractive lenticule is extracted. 8,10,11 As of the time this paper is being prepared, femtosecond LASIK and SMILE are considered to be the most widely accepted procedures by both refractive surgeons and myopic patients for the correction of refractive errors.…”

“…12 The procedure of SMILE involves the production of an intrastromal lenticule using femtosecond laser, and then this lenticule is going to be extracted through a small peripheral corneal incision, thereby, considering it as a minimally invasive refractive corneal surgery. 9,13 Although, pervious reports have shown comparable efficacy, with respect to long-term visual acuity results, between femto-LASIK and SMILE, the later operation is superior for having a number of advantages including greater corneal sensitivity, superior biomechanics, less induction of higher-order aberrations and fewer dry eye symptoms. [14][15][16][17] Probably, the major disadvantage of SMILE is the delayed optimum recovery of visual acuity following surgery in comparison with LASIK.…”

“…11,[18][19][20] SMILE offers precise visual quality and acuity and because of the enhanced patient satisfaction, the technique is increasingly being preferred for the correction of refractive errors associated with myopia and myopic astigmatism. 9 Nevertheless, SMILE has a steep learning curve and this is a challenge for beginners. 21,22 In order to familiarize the beginner surgeon to delicate procedures of SMLIE, a stepwise approach is needed and this involves observation, wetlab training, followed by flap-based refractive lenticule extraction (pseudo-SMILE).…”