Small incision lenticule extraction (SMILE) and femtosecond laser LASIK: comparison of corneal wound healing and inflammation

Abstract

Aim: To evaluate and compare early corneal wound healing and inflammatory responses after small incision lenticule extraction (SMILE) versus femtosecond laser laser in situ keratomileusis (LASIK).

Methods: Thirty-six eyes of 36 rabbits underwent SMILE, while another 36 eyes of 36 rabbits were treated with femtosecond laser LASIK. All the eyes were subjected to the same refractive correction of -6.00 DS/-1.00 DC. Twelve eyes that had no surgery were included for control. After euthanisation, corneal tissue sections were evaluated with terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick-end labelling (TUNEL) assay to detect apoptosis at postoperative 4 and 24 h, immunocytochemistry for Ki67 to detect keratocyte proliferation at postoperative day 3, week 1 and month 1, and immunocytochemistry for CD11b to detect inflammation at postoperative day 1, day 3 and week 1, respectively.

Results: No adverse effects were noted after SMILE or LASIK. Corneal healing postoperatively was uneventful in all cases. There were significantly fewer TUNEL-positive corneal stromal cells after the SMILE procedure at 4 and 24 h postoperatively (p<0.01) compared with the LASIK procedure. In addition, immunocytochemistry showed significantly fewer Ki67-positive cells in the SMILE group than those in the femtosecond laser LASIK group at day 3 and week 1 postoperatively (p<0.05), but there was little expression of Ki67 at month 1 postoperatively in both groups. The CD11b-positive cells were significantly fewer in the SMILE group at day 1, day 3 and week 1 postoperatively (p<0.01).

Conclusions: SMILE induces less keratocyte apoptosis, proliferation and inflammation compared with femtosecond laser LASIK.

Keywords: Cornea; Inflammation; Wound Healing.

Figure 1

Transferase-mediated dUTP-digoxigenin nick-end labelling (TUNEL) assay of the central cornea of different groups postoperatively. (A) 4 h after laser in situ keratomileusis (LASIK). (B) 4 h after refractive lenticule extraction (ReLEx). (C) 24 h after LASIK. (D) 24 h after ReLEx (original magnification ×400).

Figure 2

A bar graph showing the number of transferase-mediated dUTP-digoxigenin nick-end labelling (TUNEL)-positive cells in the central cornea at different time points postoperatively. The refractive lenticule extraction (ReLEx) group had significantly fewer TUNEL-positive cells at 4 and 24 h after surgery compared with the laser in situ keratomileusis (LASIK) group. **p<0.01.

Figure 3

Immunohistochemical staining for Ki67 of the central cornea of different groups postoperatively. (A) 3 days after laser in situ keratomileusis (LASIK). (B) 3 days after refractive lenticule extraction (ReLEx). (C) 1 week after LASIK. (D) 1 week after ReLEx. (E) 1 month after LASIK. (F) 1 month after ReLEx. (G) The control group (original magnification ×200).

Figure 4

A bar graph showing the number of Ki67-positive cells in the central cornea at 3 days, 1 week and 1 month postoperatively. The refractive lenticule extraction (ReLEx) group had significantly fewer Ki67-positive cells at each time point after surgery compared with the laser in situ keratomileusis (LASIK) group. *p<0.05, **p<0.01.

Figure 5

Immunohistochemical staining for CD11b of the central cornea of different groups postoperatively. (A) 1 day after laser in situ keratomileusis (LASIK). (B) 1 day after refractive lenticule extraction (ReLEx). (C) 3 days after LASIK. (D) 3 days after ReLEx. (E) 1 week after LASIK. (F) 1 week after ReLEx. (G) The control group (original magnification ×200).

Figure 6

A bar graph showing the number of CD11b-positive cells in the central cornea at 1 day, 3 days and 1 week postoperatively. The refractive lenticule extraction (ReLEx) group had significantly fewer CD11b-positive cells at each time point after surgery compared with the laser in situ keratomileusis (LASIK) group. **p<0.01.