Comparative study of small-incision lenticule extraction with and without prophylactic corneal crosslinking: 1-year outcomes

Purpose: To compare myopia and astigmatic correction after small-incision lenticule extraction (SMILE) with or without prophylactic crosslinking (SMILE Xtra).

Setting: Shenyang Aier Eye Hospital, Central South University, China.

Design: Retrospective study.

Methods: Patients with comparable manifest sphere and cylinder undergoing SMILE Xtra or SMILE were enrolled. The crosslinking (CXL) energy was 2.7 J/cm2. Only right eyes were selected. Visual and refractive changes were evaluated for 1 year. Astigmatic correction was analyzed using Alpins method.

Results: Thirty-six eyes undergoing SMILE Xtra and 40 eyes undergoing SMILE were enrolled. The uncorrected distance visual acuity at 1-day visit was lower after SMILE Xtra than that after SMILE (P = .01). At 12 months, the mean manifest refraction spherical equivalent (MRSE) and manifest cylinder were 0.08 ± 0.32 diopters (D) and -0.29 ± 0.23 D in SMILE Xtra group, whereas -0.25 ± 0.29 D and -0.22 ± 0.19 D in SMILE group (P < .01 and P = .135), respectively. Thirty-four eyes (94%) and 32 eyes (89%) in SMILE Xtra group and 36 eyes (91%) and 39 eyes (98%) in SMILE group exhibited target MRSE and manifest cylinder within ±0.50 D (P = .771 and P = .294), respectively. Compared with SMILE group, spherical correction index (SCI), correction index (CI), and difference vector were higher in SMILE Xtra group since 1-week follow-up (all P < .05). SCI and CI were slightly more than 1.0 after SMILE Xtra even at postoperative 12-month follow-up.

Conclusions: With CXL protocol of 30 mW/cm2 for 90 seconds, SMILE Xtra exhibited comparable astigmatic correction with SMILE up to 1-year follow-up, although slight spherical equivalent and astigmatic overcorrection were evident after SMILE Xtra.