Assessment of the Association Between In Vivo Corneal Biomechanical Changes After Corneal Cross-linking and Depth of Demarcation Line

PURPOSE: To test for an association between stiffening following corneal cross-linking (CXL) and demarcation line depth. METHODS: Sixty-six eyes of 66 patients treated with CXL for progressive keratoconus were included. Dynamic corneal response parameters (DCRs) were measured with the Corvis ST (Oculus Optikgerate GmbH; Wetzlar, Germany) on the day of CXL and after 1 month. Demarcation line was measured 4 weeks after CXL. A multivariate general linear model was used to test for an association between the change in DCRs and the ratio between demarcation line depth and the postoperative pachymetry. RESULTS: The authors found no significant associations between the change in inverse concave integrated radius (1/R) and the demarcation line ratio (P = .46), age (P = .33), sex (P = .11), preoperative maximum keratometry (P = .10), and laterality (P = .82). Similarly, there was no significant correlation between the change in 1/R and the demarcation line ratio (R2 = .002 and P = .75). However, there was a significant association between the preoperative values of 1/R and the respective change in 1/R (P < .0001). The change in 1/R was inversely proportional to the patient's preoperative 1/R; stiffer corneas (lower values of 1/R) were less affected than less stiff corneas (R2 = .23, P < .0001). CONCLUSIONS: CXL is associated with changes in DCRs, suggesting a change in corneal biomechanics following CXL. These changes do not appear to be associated with the demarcation line depth. [J Refract Surg. 2019;35(3):202-206.].