Lower Energy Levels Improve Visual Recovery in Small Incision Lenticule Extraction (SMILE)

PURPOSE: To compare the visual outcomes with energy close to the plasma threshold and energy at the standard set-up in small incision lenticule extraction (SMILE). METHODS: This retrospective, non-randomized, consecutive clinical case series included 486 eyes of 243 patients who underwent SMILE and were subdivided into two groups depending on the laser energy settings: the standard energy group (164 eyes) using a laser cut energy index of 36 (180 nJ), and the plasma threshold group (322 eyes) using a cut energy index of 20 (100 nJ, close to plasma threshold). A spot spacing of 4.5 µm was used in both groups. Safety, efficacy, predictability, and ocular optical quality outcomes were evaluated and compared among groups during a 3-month postoperative follow-up. RESULTS: Significantly better uncorrected (UDVA) and corrected (CDVA) distance visual acuity was found in the plasma threshold group throughout the follow-up (P ≤ .01). A higher percentage of eyes with 20/20 or better UDVA was found in the plasma threshold group at 1 day, 1 month, and 3 months postoperatively. At 1 and 3 months after surgery, no losses of two or more lines of CDVA were found in the plasma threshold group, whereas in the standard energy group these losses were observed in 3.8% and 2.7% of eyes, respectively. Significantly better postoperative modulation transfer function (P ≤ .02) and a lower level of higher order aberrations were found in the plasma threshold group compared to the standard energy group (P ≤ .025). CONCLUSIONS: An energy level close to the plasma threshold during SMILE provides a faster and better visual recovery. J Refract Surg. 2016;32(9):636-642..