Abstract
Purpose :
Supplemental oxygen during the treatment of corneal cross-linking (CXL) in patients with keratoconus was suggested to improve treatment efficiency. Using an ex-vivo porcine model, we tested the hypothesis that hyperbaric oxygen can increase intracorneal oxygen concentrations during epithelium-off and epithelium-on CXL and enhance the effects of CXL.
Methods :
CXL was performed using riboflavin and UV-A irradiances of 3 mW/cm2 on porcine corneas under normobaric and hyperbaric conditions in a hyperbaric treatment chamber, both with and without supplemented oxygen, on epithelium-off (n=10 per treatment group) and epithelium-on groups (n=5 per treatment group). Intracorneal oxygen concentrations were measured during irradiation. Biomechanical properties in terms of tensile and compression tests as well as corneal resistance to enzymatic digestion with 0.01 U/ml Collagenase A were chosen as efficacy outcomes. Untreated porcine corneas (n=10 epithelium-off, n=5 epithelium-on) served as controls. Analyses of variance were used for statistical evaluation.
Results :
Considering both epithelium-off and epithelium-on corneas respectively, the mean intracorneal oxygen concentrations differed significantly (p<0.05) among the treatment groups. Intracorneal oxygen concentrations could be improved from 6.9±4.3% and 8.6±3.6% under standard normobaric conditions to 34.6±15.3% and 26.6±12% in groups cross-linked under hyperbaric oxygen conditions. Biomechanical properties showed no statistically significant differences between the treatment groups. Mean enzymatic digestion time increased significantly from 3±0 days in the normobaric to 5.4±1.7 days in the hyperbaric epithelium-off group.
Conclusions :
While hyperbaric oxygen conditions increase intracorneal oxygen concentrations during CXL regardless of the specimens’ epithelial condition, they did not affect the biomechanical properties of full thickness porcine corneas. However, as the effect of CXL is usually limited to the anterior 400 μm of corneal tissue and since the average porcine cornea is around 800–900 μm thick, we may have easily missed any stiffening effect in our model. An increased resistance to enzymatic digestion after hyperbaric epithelium-off CXL suggests that an effect is likely and that potential advantages of hyperbaric oxygen during CXL should be further assessed on thinner specimens.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.