Corneal Biomechanical Properties before and after Collagen Cross Linking in Keratoconus

Aim of Study: The aim of this study is to analyze the changes in the biomechanical properties of the cornea after collagen cross linking in eyes with progressive keratoconus through the assessment of corneal hysteresis and corneal resistance factor before and after the procedure. Methods: Thirty eyes of 22 patients with mean age 24.56± 3.79 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). Patients were assessed with ORA preoperatively, at 1 and 6 months after treatment. Postoperative measurements at each visit were compared with preoperative values. Demarcation line and corneal haze were also assessed after cross linking procedure. Results: CH was decreased after cross linking treatment, with the difference not statistically significant at 1 and 6 months p-value=0.61 and 0.198 respectively. CRF was elevated at 1 and 6 months after CXL and was statistically significant at 6 months (p=0.005). Conclusion: After collagen cross linking no significant change in corneal hystresis occurred at 1 and 6 months. Increase in corneal resistant factors occurred and was statstically significant at 6 months.