Can we measure corneal biomechanical changes after collagen cross-linking in eyes with keratoconus?-A pilot study

PURPOSE: To assess changes in biomechanical properties of human cornea after treatment of keratoconus with UV-A-riboflavin corneal collagen cross-linking (CXL). DESIGN: Single-center, prospective, interventional study. METHODS: Ten eyes of 10 patients aged 26.5 ± 5.7 (mean ± SD) years with progressive keratoconus were treated with UV-A-riboflavin CXL and assessed with the Ocular Response Analyzer (ORA) that measured corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg), and corneal compensated intraocular pressure (IOPcc). Intraocular pressure was also measured by Goldmann applanation tonometry (GAT-IOP). Patients were assessed with ORA preoperatively, at week 1, months 1, 3, and 6 after treatment. Postoperative measurements at each visit were compared with preoperative values. RESULTS: CH and CRF were transiently elevated after cross-linking treatment, with the difference not statistically significant (P > 0.3). IOPcc and IOPg were statistically significantly higher at 1 week and 1 month but not subsequently (P < 0.04). GAT-IOP was statistically significantly higher at 1 week and at 1 and 3 months (P < 0.01). CONCLUSIONS: There were no significant differences in corneal biomechanical properties, as measured with the ORA parameters CH and CRF, after CXL in keratoconus. IOPcc, IOPg, and GAT-IOP values were transiently elevated after CXL treatment in our study. Whether this reflects a measurement artifact resulting from corneal changes or true elevation of intraocular pressure is unclear.