Identification Of Safe Treatment Protocols For Effective Crosslinking Of The Peripheral Cornea – An Experimental Study.

To test modified corneal crosslinking (CXL) protocols improve possible beneficial effects on the peripheral cornea regarding long term corneal transplant stability, corneal neovascularization and lymphatic vessels. This trial evaluated modified CXL treatment protocols on peripheral human donor corneas.

Department of Ophthalmology, Medical University of Vienna, Vienna Austria

Peripheral CXL (pCXL) was performed within a ring of 9-11mm of 36 human donor corneas with variations in applied energy (5.4 J/cm², 7.2 J/cm², 10 J/cm²) at 9 mW/cm² irradiance. Each energy level was additionally modulated regarding oxygen level surrounding the cornea during treatment (21%; 100%). Stress-strain tests with endpoints at 12% strain and Collagenase-A assisted digestions to complete digestion were performed to evaluate the rigidity and resistance of treated and control tissue. Further, corneas were processed histologically via TUNEL assay and H&E staining in order to demonstrate the effects on stromal cells during treatment under varying CXL conditions.

Higher energy levels, particularly with supplementary oxygen showed significant increases in the biomechanical stability, resistance to digestion as well as DNA strand breakage and depth of relative keratocyte scarcity.

Increases in energy and supplemental oxygen improved CXL effect, though endothelial safety could not be verified with confidence in high-fluence CXL with supplemental oxygen. Results suggest that CXL protocols using 7.2 J/cm² with 100% O2 or 10 J/cm² without supplemental oxygen prove most effective without anticipated risk of endothelial damage.