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A. P. Soendergaard, A. Ivarsen, J. Hjortdal; Corneal Hydration and Swelling Properties Following Uva Riboflavin Collagen Cross-Linking. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4982.
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To evaluate the effect of UVA riboflavin collagen cross-linking on hydration and swelling properties of porcine corneas.
In porcine eyes, the central corneal thickness (CCT) was determined by ultrasound pachymetry. The treatment group was treated using the standard UVA riboflavin cross-linking procedure (CXL). The central 8 mm cornea was the trephined and the weight measured. In the control group neither riboflavin solution nor UVA light was applied. The swelling of the corneal buttons in a saline bath were measured in a custom engineered biomechanical setup. The force exerted by the corneas during swelling in the anterior-posterior direction was measured at different thicknesses (-5%, +10% and +20% of initial CCT). Finally, corneas were freeze-dried to determine dry weight and calculate changes in hydration.
No significant difference in mean dry weight was observed (p=0.735) between groups. A significant reduction of central corneal thickness after treatment was observed in the CXL group (p<0.001, paired t-test), and hydration in the CXL group was significantly lowered by 168%, (95%CI: -284;-53) compared to the control group (p=0.009). The swelling force (SF) in all phases was significantly higher in the CXL group than in the control group, but this difference could be explained by the significant decrease in corneal thickness and hydration. Comparing linear regressions of CCT and swelling force in the groups showed a significant difference (p<0.001).
The CXL treatment appears to reduce the central corneal thickness significantly, thereby dehydrating the stroma significantly. The swelling force of the stroma increases significantly in the CXL group, but the difference in CCT fully explains this surprising finding. At similar corneal hydration CXL treated corneas appear to have a lower swelling pressure than untreated corneas, indicating that CXL treatment can reduce corneal edema in vivo.
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