Corneal biomechanical and tomographic outcomes following accelerated cross-linking in keratoconus: a focus on cone localization.

PURPOSE: To evaluate the biomechanical and tomographic characteristics of keratoconic corneas undergoing accelerated cross-linking (CXL) for over one year and to assess the impact of cone localization on postoperative biomechanical behavior.

STUDY DESIGN: Prospective-comparative.

METHODS: This study included 68 eyes of 68 patients with progressive keratoconus. Based on cone location, the patients were divided into two groups: group 1 (central cone; 34 eyes) and group 2 (paracentral cone; 34 eyes). Scheimpflug imaging was used to assess the corneal thickness, anterior and posterior Kmean, Kmax, and astigmatism. The Ocular Response Analyzer (ORA) measures corneal compensated intraocular pressure (IOPcc), Goldmann-correlated pressure (IOPg), corneal hysteresis (CH), and corneal resistance factor (CRF). All the baseline measurements were repeated at 1, 6, and 12 months. Demarcation line (DL) depth was assessed at 1 month using anterior segment optical coherence tomography. Best corrected visual acuity was recorded at each visit.

RESULTS: At 1year, anterior Kmean, posterior Kmean and Kmax showed significant reductions (p < 0.01). No significant differences in CH or CRF changes were found between the central and peripheral cones (p = 0.22, p = 0.33). Visual improvement and reduction in spherical equivalent were greater in the central cone group (p = 0.03, p = 0.03). DL depth correlated positively with CH and CRF at 1 month (p = 0.02, p = 0.008), but not at 1 year.

CONCLUSION: Accelerated CXL improves corneal shape, but may not produce detectable changes in ORA-derived biomechanics. Regional stiffening may not be captured by global indices, and the cone location appears to be more influential on visual recovery than biomechanical parameters.