Predictability of SMILE over four years in high myopes

To determine whether the visual outcomes of the refractive surgery technique small incision lenticule extraction (SMILE), are stable, effective, and predictable for high myopia over a four-year period.

This is a retrospective study. The data were collected between March 2012 and July 2016.

Two hundred and forty-eight patients participated in the study; that is, 496 eyes: 140 eyes of 70 patients (52 women/18 men) were classified into the highly myopic group (refraction measured in spherical equivalent (RMSE)>-6 D), and 356 eyes of 178 patients (98 women/80 men) into the control group (RMSE<-6 D). Follow-up tests were conducted immediately following the procedure (D+1), after three months, after one year, and after four years. Refraction, uncorrected visual acuity (UCVA), and best visual corrected acuity (BCVA) were measured. The highly myopic group (HMG) contained more women, and astigmatism was higher for this group than for the control group (CG).

These were BCVA, refractive stability, the index of safety (SI: BCVA preoperatively D+1/BCVA postoperatively), and predictability (the percentage of eyes within±0.5 D of the target).

In both groups, UCVA was better after the fourth year than it was immediately after the procedure (HMG: P=0.001; CG: P=0.001). Although it differed at one year (P=0.01), the groups' refractive stability tended to converge over four years (P=0.138). The groups' SI was found to be identical in the four follow-up tests (P=0.734 at D+1; P=0.07 at M+1; P=0.160 at M3 and Y1; and P=0.274 at Y4). For the HMG, SI stability was attained after three months (1.00±0.1); whereas it was attained after one month (0.91±0.11) for the CG. Four years after the surgery, we observed that 87% of the operated-upon eyes in the HMG were within 0.5 D of the target.

SMILE is a good refractive surgery technique for treating high myopia. It yields stable, safe, effective, and predictable results over four years.