Corneal Hysteresis before and after Corneal Collagen Cross Linking for Keratoconus

Background: Corneal collagen cross-linking (CXL) has been used as a treatment option in patients with either keratoconus or iatrogenic corneal ectasia after LASIK. The purpose of corneal cross-linking is to stabilize the corneal stroma and to delay the progression of these two pathologic entities. Objective: The aim of this study is to compare the corneal hysteresis before and after corneal collagen cross-linking using riboflavin and ultraviolet-A light by the epithelial-off technique for treatment of keratoconus. Patients and methods: This study is a single-centre prospective interventional study. It was conducted between April 2018 to December 2018 and included 30 eyes of 18 patients with a mean age 27.08 years (range from 17- 30). They were 12 female eyes and 18 male eyes; all underwent corneal collagen cross-linking using riboflavin and ultraviolet-A light at Kobry El Kobba Military Specialized Eye Hospital. Results: All patients were evaluated preoperatively for their uncorrected corrected visual acuity (UCVA), best corrected visual acuity (BCVA), k-reading, spherical equivalent and pachymetry (using Pentacam), and corneal biomechanical properties (using ocular response analyzer (ORA). The mean age was 27.08±7.86 years, and postoperative follow up was at 1 and 4 months. The mean CH was 7.93±1.79 mmHg preoperatively, 8.27±1.22 mmHg at 1 month, 8.99±1.24 mmHg at 4 months, which show a statistically significant increase in the mean CH pre- and postoperatively, while CRF the other parameter, show a highly statistically significant decrease pre- and postoperatively. Conclusion: CXL is a promising new treatment modality for keratoconus patients and may affect corneal biomechanics.