Corneal Collagen Crosslinking Oxygen Dependency

Hammer, Arthur

Corneal Collagen Crosslinking Oxygen Dependency

Sunday, April 27, 2014: 3:46 PM

Room 151B (Boston Convention and Exhibition Center)

Arthur Hammer, MD, Geneva University Hospitals, Gneva, Switzerland

Olivier Richoz, MD, Geneva University Hospitals, Geneva, Switzerland

Samuel Arba Mosquera, PhD, SCHWIND eye-tech-solutions, Kleinostheim, Germany

Zisis Gatzioufas, MD, University Hospitals Geneva, Geneva, Switzerland

Farhad Hafezi, MD, PhD, Geneva University Hospitals, Geneva, Switzerland

Narrative Responses:

Purpose
Recent CXL protocol modifications include shorter irradiation times at higher fluences. However the limits of reciprocity are unknown regarding corneal biomechanical properties. Limitations in the corneal oxygen diffusion capacity and its potential impact on the efficacy of CXL raise concerns regarding the efficiency of high-fluence CXL and of transepithelial CXL.

Methods
Porcine corneas were treated with an epithelium-off CXL at a fluence of 9 mW/cm² under two different atmospheres: one with a regular oxygen content (21 %) and another in a helium-supplemented, low-oxygen environment (< 0.1%). Untreated corneas served as controls (n=20 each). 5 mm corneal stripes were prepared and biomechanical stiffness was measured using an extensometer.

Results
Corneas cross-linked under normal oxygen levels showed a significant increase in biomechanical stability (14.36 MPa ± 2.69 SD), whereas corneas treated similarly, but in a low-oxygen atmosphere showed a Young’s modulus similar to untreated controls (11.72 MPa ± 2.77 SD).

Conclusion
The biomechanical effect of CXL seems to be oxygen-dependent. This dependency will be of particular importance in high-fluence and transepithelial CXL and will most likely require major protocol modifications to maintain the efficiency of the method.