Influence of age on small incision lenticule extraction outcomes

Purpose To evaluate the influence of patient's age at the time of surgery on small incision lenticule extraction (SMILE) refractive outcomes. Methods This is a retrospective, consecutive, comparative study. We compared the refractive outcomes after myopic SMILE from two groups of patients divided by age (patients <= 35 and >= 40 years old). All eyes were evaluated preoperatively and at 1 and 6 months postoperatively. Main outcome measures were differences on efficacy, safety, predictability and astigmatic changes by vector analysis with ASSORT software between both study groups. Results 102 matched eyes of 53 patients were included. Preoperatively, we evidenced no differences in the mean SE or astigmatism between groups. However, 6 months postoperatively we observed a significantly worse mean astigmatism (p=0.019), while not regarding SE, in the older population, with a trend towards undercorrection of the refractive cylinder in the >= 40 group. We also observed a statistically significant difference in the efficacy (0.86-1 month and 0.97-6 months in >= 40group vs 0.97-1 month and 1.07-6 months in the <= 35 group; p=0.003) and safety indexes (0.93-1 month and 1.04-6 months in >= 40 group vs 1.0-1 month and 1.11-6 months in the <= 35 group; p=0.008) at 6 months among groups. Conclusions Post-SMILE refractive outcomes in those patients over 40 years of age, although acceptable, are not as good as those obtained in younger patients, showing a significantly lower efficacy and safety indexes, and poorer astigmatic outcomes, with a tendency towards undercorrection. We hypothetise that the increased corneal stroma stiffness in the aged group modifies the post-SMILE corneal stroma remodelling capacity, thus affecting the SMILE refractive and visual response.