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Hyperbaric Oxygenation Increases Available Oxygen and Resistance to Enzymatic Digestion in Accelerated Corneal
Johannes Menzel-Severing1, Theresa Streit1, Jule Schmiedel1
1Department of Ophthalmology, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University Düsseldorf, Düsseldorf, NRW, Germany.
Purpose:
The present study aimed to determine whether hyperbaric oxygenation increases intrastromal oxygen concentration during accelerated corneal collagen crosslinking (CXL) and whether this enhances CXL effects.
Methods:
Oxygen concentration was measured in porcine corneas during epithelium-off CXL with UV-A intensity of 9 mW/cm2 for 10 minutes. Experiments were performed under normobaric and hyperbaric (2.4 bar) conditions, with and without supplemental oxygen. Stromal resistance to lysis by collagenase A and biomechanical changes were measured.
Results:
Oxygen concentrations before irradiation averaged 11% in the normobaric group (CXLnorm), 37% in the normobaric group with supplemental oxygen (CXLnorm + O2), 13% in the hyperbaric group (CXLhyp), and 43% in the hyperbaric group with supplemental oxygen (CXLhyp + O2). After the onset of UV-A, oxygen concentration decreased to 1.5% in CXLnorm, 3% in CXLhyp, 21% in CXLnorm + O2, and 38% in CXLhyp + O2. Differences between groups were statistically significant (P < 0.0001). Corneal lenticules from the CXLhyp + O2 group were completely digested by collagenase after 5.4 days (standard deviation = 1.34). This was significantly later (P < 0.05) than in other groups. Biomechanical testing did not reveal meaningful differences between the treatment protocols.
Conclusions:
These data suggest that hyperbaric oxygenation increases intrastromal oxygen in porcine corneas, ensuring constant availability during accelerated CXL. This leads to enhanced resistance to collagenase digestion of anterior corneal stroma.
Translational Relevance:
More intrastromal oxygen and resistance to proteolytic enzymes may make CXL with hyperbaric oxygenation an improved treatment for progressive keratoconus and (infectious) corneal ulcers.
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