Comparing Corneal OCT Findings in High Irradiance Corneal Crosslinking Combined with Femtosecond Laser In Situ Keratomileusis versus Femtosecond Laser In Situ Keratomileusis

Objective: To study Corneal OCT findings in the interface and the demarcation line under or over the interface in patients that undergo Femtosecond laser in situ Keratomeulisis compared to patients that undergo Femtosecond laser in situ Keratomeulisis combined with high irradiance corneal cross linking (Femto-Lasik Xtra). Study Design: Prospective Randomized Comparative Study. Methods: Our study included 40 eyes of 20 patients divided into 2 groups, a group of 10 patients with 20 eyes underwent Femto-Lasik & the other group of 10 patients of 20 eyes underwent Femto-Lasik Xtra. The Femto Lasik procedure was done using Alcon Wave Light FS200 laser machine. The Femto-Lasik XTRA procedure entails the administration of half fluence high irradiance cross-linking subsequent to refractive correction. A higher concentration 0.25% riboflavin is applied on the stromal bed and the flap subsequent to laser ablation with a soak time of 90 seconds, UV-A irradiance is delivered as a homogenous beam of 30 mW/cm2 for 90 s to deliver a total fluence of 2.7J/cm2. Patients were randomly observed and HEIDELBERG ASOCT was performed after 1 week, 1 month & 3 months post-operative. Results: A demarcation line was noted in femto Lasik Xtra patients, appeared more evident in the peripheral cornea and faded as it approached the central cornea. It became less evident after 1 month and 3 months period respectively. Also the flap hinge was more hyper reflective and evident in femto Lasik Xtra patients when compared to femto Lasik patients. Anterior crosslinked stroma appeared more hyper reflective than posterior stroma in femto Lasik Xtra patients. Flap edge was also more hyper reflective and better demarked in femto Lasik Xtra treated corneas when compared to femto Lasik treated corneas. Conclusion: AS-OCT showed significant differences between femto Lasik and Femto Lasik Xtra treated corneas. Significant changes were noted in the demarcation line in Femto Lasik Xtra patients along different time periods post-operative.