Comparing Efficacy and Corneal Biomechanics Between KLEx and KLEx Xtra in High Myopia: A 1-Year Prospective Randomized Study

Abstract Introduction This work aims to compare the 12-month changes in refractive outcomes, safety, efficacy, predictability, corneal biomechanics, and corneal topography between keratorefractive lenticule extraction (KLEx) and KLEx combined with prophylactic corneal collagen cross-linking (KLEx Xtra). Methods A prospective, randomized, controlled trial was conducted with 80 eyes in each group. The primary endpoint was the manifest refraction spherical equivalent (MRSE) at 12 months postoperatively in both groups. Secondary endpoints included visual outcomes, corneal biomechanical parameters, and topographic changes. The study has been registered at ClinicalTrials.gov (No. NCT06992011). Results At the 12-month follow-up, a small statistically significant difference in MRSE was observed between the two groups (KLEx Xtra: − 0.02 ± 0.38 D and − 0.17 ± 0.35 D, p = 0.047). Both groups demonstrated comparable and favorable safety and efficacy indices at 12 months. While corneal haze occurred universally early after the CXL procedure, it persisted in a subset of eyes for up to 6 months. At 12 months postoperatively, both KLEx and KLEx Xtra groups showed significant changes in corneal biomechanical parameters. The KLEx Xtra group exhibited enhanced biomechanical strength, with a significant improvement in parameters such as first applanation velocity (A1 V), Corvis biomechanical index (CBI), stiffness parameter at applanation 1 (SP-A1), and stress–strain index (SSI), compared to the KLEx group at 12 months postoperatively (p < 0.05). There were no significant differences between the two groups in corneal topographic parameters up to 6 months postoperatively, but at 12 months, the KLEx group showed significantly higher steep K value of anterior corneal surface (K2 F) compared to the KLEx Xtra group. Conclusions KLEx Xtra demonstrates superior refractive accuracy with a reduced risk of myopic regression within 12 months of follow-up while also enhancing corneal biomechanical strength, making it a viable alternative for people with high myopia. Trial Registration The study has been registered at Clinicaltrials.gov, NCT06992011 (retrospectively registered at May 7, 2025).