Interface bonding with corneal crosslinking (CXL) after LASIK ex vivo

PURPOSE. Interface bonding with corneal crosslinking (CXL) after LASIK using two different photosensitizers was studied ex vivo. METHODS. A LASIK flap was created in enucleated rabbit eyes using a femtosecond laser. After the dissection, CXL was performed to seal the interface. In one group interface CXL was performed using rose bengal and green light, whereas in a second group riboflavin and UV-A light was used. In both groups irradiance, radiant exposure, dye concentration, and imbibition time was varied. In a control group, LASIK only was performed. After the procedures, the maximal shear-force required to separate the flap from the stroma was measured. Additionally, corneal transmission spectra were recorded. RESULTS. Optimized parameters for rose bengal/green-light bonding lead to a 2.1-fold increase in shear-force compared with untreated control eyes (P < 0.01). The optimal parameter combination was: irradiance of 180 mW/cm² for 14 minutes (total radiant exposure 150 J/ cm²), rose bengal concentration 0.1%, and an imbibition time of 2 minutes. Optimized riboflavin/UV-A light parameters were 0.5% for 2 minutes with a radiant exposure of 8.1 J/cm² obtained by an irradiance of 30 mW/cm² for 4.5 minutes. These optimized parameters lead to a 2-fold increase compared with untreated control eyes (P < 0.01). Optical transmission experiments suggest safety for more posterior structures. CONCLUSIONS. Based on ex-vivo results, interface bonding after LASIK using crosslinking with either rose bengal or riboflavin increases the adhesion between flap and stromal bed. In vivo trials are needed to evaluate the temporal evolution of the effect.