LASIK following Small Incision Lenticule Extraction (SMILE) Lenticule Re-Implantation: A Feasibility Study of a Novel Method for Treatment of Presbyopia

Abstract

Presbyopia remains a major visual impairment for patients, who have previously undergone laser refractive correction and enjoyed unaided distance vision prior to the onset of presbyopia. Corneal stromal volume restoration through small incision lenticule extraction (SMILE) lenticule re-implantation presents an opportunity for restoring the patients’ non-dominant eye to previous low myopia to achieve a monovision. In this study, we investigated the feasibility of performing LASIK after lenticule re-implantation as a method to create presbyopic monovision. A -6.00D SMILE correction was performed in 9 rabbit eyes. The lenticules were cryopreserved for 14 days and re-implanted. Five weeks later, 3 of these eyes underwent LASIK for -5.00D correction (RL group); 3 underwent LASIK flap creation, which was not lifted (RN); and no further procedures were performed on the remaining 3 eyes. These groups were compared with 3 eyes that underwent standard LASIK for a -5.00D correction (LO); 3 that underwent creation of non-lifted flap (LN); and 3 non-operated eyes. Rabbits were euthanized 1 day post-surgery. Tissue responses were analyzed by immunohistochemistry, slit lamp and in vivo confocal microscopy (IVCM). Intrastromal irregularities and elevated reflectivity levels of the excimer-ablated plane were observed on slit lamp and IVCM, respectively in the RL group. The results were comparable (P = 0.310) to IVCM findings in the LO group. RL and LO groups showed similar fibronectin expression levels, number of CD11b-positive cells (P = 0.304) and apoptotic cells (P = 0.198). There was no difference between the RN and LN groups in reflectivity levels (P = 0.627), fibronectin expression levels, CD11b-positive cells (P = 0.135) and apoptotic cells (P = 0.128). LASIK can be performed following lenticule re-implantation to create presbyopic monovision. The tissue responses elicited after performing LASIK on corneas that have undergone SMILE and subsequent lenticule re-implantation are similar to primary procedure.

Small Incision Lenticule Extraction (SMILE)

“…During the following 1-2 weeks, the increased fi bronectin provided a provisional matrix to support the a b c d migration of the remaining epithelial cells or keratocytes to cover the area of the defect [ 33 , 34 ]. After 2 weeks, the wound-healing response was complete, and the expression of fi bronectin began to decrease [ 33 ]. This explains why the expression of fi bronectin appeared more distinct around both the small vertical incision and extracted lenticule plane at week 1 after SMILE.…”

“…This study highlighted the importance of a fl ap-less procedure to favor a rapid nerve restoration; however, it does not take into account the early postoperative phase, and the LASIK technique was not investigated. Another investigation used in vivo confocal microscopy to evaluate changes of corneal innervation following SMILE surgery as compared to Fs-LASIK-treated eyes [ 33 ]. It reported a decrease in subbasal nerve fi ber density less severe after SMILE in comparison to Fs-LASIK in the early postoperative phase (1 week to 3 months), while nerve density reached similar values at 6 months following both procedures.…”

“…Peripheral stromal expansion is caused by the relaxation of severed stromal collagen lamellae, so it would be expected to fi nd less stromal expansion after SMILE as fewer lamellae are cut, and hence, it would be expected for less spherical aberration to be induced. In a recent study [ 33 ], we compared the induction of spherical aberration between SMILE, where the refractive lenticule is only minimally aspheric, and LASIK using the MEL80 with the Laser Blended Vision module [ 29 ], which uses a nonlinear aspherically optimized ablation profi le. The LASIK group was matched by refraction to within ±0.25 D and all eyes were treated with a 6 mm optical zone in both groups.…”

“…To demonstrate this, we retrospectively applied the model to our initial SMILE case series ( n = 96) and compared the postoperative total tensile strength to a control group of LASIK eyes matched for refraction (±0.25 D) and pachymetry (±20 μm) [ 33 ]. Optical zone was not part of the matching criteria, so that the populations represented routine clinical use of the two procedures.…”

New Developments in the Lenticule Extraction Procedure

“…51 Other studies in rabbits and primates have shown successful cryopreservation and later re-implantation of a stromal lenticule. [52][53][54][55] Furthermore, in primates, the procedure was shown to induce little postoperative wound repair, and keratocyte repopulation could be observed after 16 weeks. 52 Although further studies are needed, lenticule re-implantation or transplantation from one patient to another may become reality in the near future.…”