Optimal Parameters of Scanning Mode in Small Incision Lenticule Extraction (SMILE): Clinical Results and Ultrastructural Analysis.

Abstract

To compare the effect of two scanning modes with different femtosecond laser settings on clinical outcomes and ultrastructural analysis of the lenticule surface in small incision lenticule extraction (SMILE). A total of 78 eyes from 39 consecutive patients were included with the standard scanning mode (energy level of 105 nJ vs spot distance of 3 mm) in one eye and the fast scanning mode (energy level of 110 nJ vs spot distance of 4.5 mm) in the other eye, all eyes being randomly assigned. Patients received complete ophthalmic examinations preoperatively and at different follow-up visits after SMILE. Ten human corneal lenticules were analyzed using scanning electron microscopy. Uncorrected distance visual acuity at 1 day and 1 week postoperatively was -0.06 ± 0.10 and -0.11 ± 0.05 logMAR, respectively, in the fast scanning group, which was significantly better than in the standard scanning group (-0.11 ± 0.08 and -0.12 ± 0.05 logMAR, respectively), and no significant difference was found between the groups at 1 and 3 months. The contrast sensitivity was higher at different time points in the fast scanning mode group compared with the standard scanning group (all P < .05). Ultrastructurally, the corneal lenticules from the fast scanning group showed a smoother surface than those from the standard scanning mode group qualitatively and quantitatively (all P < .001). SMILE using the fast scanning mode facilitates better visual acuity with improved contrast sensitivity in the early postoperative period. Experimental studies on the ultrastructure of corneal lenticules support these clinical results. [J Refract Surg. 2020;36(1):34-41.].