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Anders P. Soendergaard, Anders Ivarsen, Jesper Hjortdal; Swelling Pressure Changes After Corneal UVA Riboflavin Collagen Cross-linking. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5210.
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To evaluate whether UVA riboflavin cross-linking reduces stromal swelling pressure in porcine corneas.
In 34 porcine eyes, the central corneal thickness (CCT) was determined by ultrasound pachymetry. The treatment group (n=17) was treated using the standard UVA riboflavin cross-linking procedure (CXL), applying riboflavin solution for 30 minutes followed by a 30-minute UV-A radiation under continued riboflavin administration. In the control group (n=17) only riboflavin solution was applied. The central 8 mm cornea was the trephined and the weight measured. The swelling of the corneal buttons in isotonic saline was measured in a custom engineered biomechanical setup. The force exerted by the corneas during swelling in the anterior-posterior direction was recorded at different thicknesses (-5%, +5%, +10%, +20% and +30% of initial CCT) and the swelling pressure calculated. Dry weights were obtained for solids correction.
No significant difference in mean dry weight was observed between groups. A non-significant reduction of central corneal thickness after treatment was observed in the CXL group (p = 0.815), and in the hydration change in the CXL group compared to the control group (p = 0.200). Linear regressions of CCT and swelling force were not significantly different in the two groups.
The results obtained, when testing full thickness corneal buttons, may not detect the changes induced by CXL, since only the anterior segment of the stroma is cross-linked. Segmental testing is currently conducted to detect differences in the anterior vs. posterior stroma. Preliminary data suggest that the swelling pressure is reduced in the anterior approximately 200µm stroma in the treatment group, indicating that CXL treatment can reduce corneal edema in vivo.
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