Does Age Influence Corneal Transparency After Klex? Quantitative Densitometry Outcomes

SMILE, the first keratorefractive lenticule extraction (KLEX) procedure, is well established, with more than 13 million procedures performed worldwide. Given the broad spectrum of candidates undergoing SMILE, postoperative corneal clarity and interface transparency show clinically observable variability. In clinical practice, age is suspected to influence wound healing behavior and may be associated with subtle, subclinical interface findings. This study was designed to objectively evaluate the effect of age on postoperative corneal transparency using quantitative densitometry, while minimizing confounding through matching relevant preoperative and perioperative factors.

Retrospective cohort study including patients who underwent SMILE between 2014 and 2025 at the Department of Ophthalmology, Ludwig Maximilian University of Munich, and the SmileEyes eye clinics in Munich, Germany.

From a cohort of more than 10,000 eyes undergoing SMILE during the study period, eyes were stratified by age at surgery into eight groups: 18–25, 26–30, 31–35, 36–40, 40–45, 46–50, 50–55, and >55 years. Within these strata, potential confounders were controlled through matching, including surgeon, VisuMax laser delivery parameters (spot size, spot/track spacing, and pulse energy), and the postoperative medication regimen. The large underlying dataset enabled selection of eyes with comparable preoperative refractive error, with matching for manifest refraction spherical equivalent (MRSE) within each age group. Corneal transparency was quantified using Scheimpflug-based Pentacam HR densitometry, analyzing the anterior 120 µm of the cornea.

A total of 564 eyes were analyzed across the eight age strata. Mean anterior stromal densitometry differed significantly in patients aged ≥46 years, whereas the 40–45-year group showed a numerically higher value without statistical significance.Pairwise comparisons of age groups at each follow-up time point were performed using estimated marginal means with Tukey-adjusted post-hoc testing to control for multiple comparisons. The between group separation was most pronounced at postoperative week 6; at 1-year, significant differences persisted only in the ≥46-year strata. Confidence intervals widened progressively with age, indicating greater inter-individual variability and a small subset of older eyes with marked densitometry outliers.

Our findings support age as an important determinant of postoperative corneal transparency after SMILE, with patients of certain age threshold demonstrating higher anterior stromal densitometry and greater inter individual variability. These results may have practical implications for patient selection, optimizing procedure planning, and in particular, support age-tailored postoperative follow-up and medication regimen.