Optics & Refraction

Age A Factor in Refractive Outcomes of SMILE Procedure

Avatar photoErin Boyle
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New Vision clinic, main center for refractive surgery in France, with cutting-edge technology for all eye laser operations. Eye operation using the SMILE, Small Incision Lenticule Extraction, laser technique. It is a new generation of treatment which enables short-sightedness to be corrected without removing the superficial layer of the cornea, nor opening it. The SMILE technique involves producing with the Femtosecond laser, a lenticule, thin slice, in 3D in the thickness of the cornea, and removing it with a micro incision in the shape of a smile. The worse the short-sightedness, the thicker the lenticule. (Photo by: BSIP/Universal Images Group via Getty Images)
Researchers identified outcome metrics that vary between 2 age groups.

In patients older than 40 years, small incision lenticule extraction (SMILE) refractive procedures may have significantly lower efficacy and safety indexes, poorer astigmatic outcomes, and a tendency toward undercorrection than in patients younger than 35, according to a study published in the British Journal of Ophthalmology. 

The retrospective, consecutive, comparative study looked at the influence of a person’s age on refractive outcomes at the time of myopic SMILE. Researchers compared results of 102 matched eyes of 53 patients divided into 2 groups by age (those 35 years and younger, and those 40 years and older), preoperatively and 1 and 6 months postoperatively. Efficacy, safety, predictability, and astigmatic changes were the main outcome measures, taken by vector analysis. 

No differences in mean spherical equivalent or astigmatism were found between groups preoperatively. But at 6 months postoperatively, investigators discovered that mean astigmatism (P =.019) was significantly worse in the older population, which also had more undercorrection of the refractive cylinder. At 6 months, they also saw a statistically significant difference in efficacy (0.86 at 1 month and 0.97 at 6 months in ≥40 group vs 0.97 at 1 month and 1.07 at 6 months in the ≤35 group; P =.003) and safety indexes (0.93 at 1 month and 1.04 at 6 months in ≥40 group vs 1.0 at 1 month and 1.11 at 6 months in the ≤35 group; P =.008).

The researchers say SMILE is an “efficient, safe, stable, and relatively predictable refractive surgery solution for the management of myopia with or without mild to moderate astigmatism” for patients older than over 40. However, they caution that surgeons might see worse refractive outcomes in older patients than in younger patients. 

“We hypothesize that the increased corneal stroma stiffness in the aged group modifies the post-SMILE corneal stroma remodeling capacity, thus affecting the SMILE refractive and visual response,” the researchers conclude.

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The study’s limitations include its retrospective design and possible paired date bias from both patient’s eyes being included in the study (but they did so, they report, because they wanted to expand the study’s sample size). “Nevertheless, further studies with larger samples and without this potential bias are required in order to confirm these outcomes.” 

Reference

Primavera L, Canto-Cerdan M, Alio J, Alio del Barrio JL. Influence of age on small incision lenticule extraction outcomes. BriJ Ophthalmol. Published online November 18, 2020. doi: 10.1136/bjophthalmol-2020-316865

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