A recent study investigating SMILE outcomes found that the procedure has significantly lower efficacy and safety in presbyopic patients than in younger ones. Older corneas respond differently to SMILE because stromal stiffness increases with age, the researchers wrote in their paper. “As a consequence, corneal remodeling and biomechanical response to the lenticule extraction could differ among corneas with different underlying strength and stiffness.”

The retrospective, consecutive, comparative study included 102 eyes of 53 patients who underwent SMILE for myopia. Patients were divided into two groups: those 35 and younger and those 40 and older. Follow-up evaluations were conducted at one and six months postoperatively.

Upon preoperative exam, the researchers found no differences in mean spherical equivalent or astigmatism between the groups. At six months, however, they observed significantly worse mean astigmatism—disregarding spherical equivalent—in the older population. The trend showed an undercorrection of refractive cylinder.

In terms of efficacy, the researchers noticed a statistically significant difference between the groups. The older group demonstrated efficacy indices of 0.86 at one month and 0.97 at six months, while the younger group showed 0.97 at one month and 1.07 at six months. Safety indices showed similar significant trends: 0.93 at one month and 1.06 at six months in the older group, compared with 1.00 at one month and 1.11 at six months in the younger group.

The researchers concluded that in addition to poorer efficacy and safety indices, the SMILE outcomes in older patients are accompanied by poorer astigmatic outcomes, with a tendency toward undercorrection. They believe this difference in age is related to increased corneal stiffness, which affects the SMILE refractive and visual responses.