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X. He, E. Spoerl, J. Liu; Ultrasonically Detected Changes in Corneal Properties Due to Riboflavin-UVA Induced Collagen Crosslinking. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5476.
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To determine the changes in corneal properties induced by riboflavin-ultraviolet A (UVA) irradiation using a non-invasive quantitative ultrasound method in a porcine eye model.
Twenty-eight fresh porcine globes were acquired within 24 hours post-modern. The porcine globes were divided into two groups: the collagen-crosslinking (CXL) group (n=14) that were irradiated with UVA after riboflavin application following the standard protocol, and the control group (n=14) that underwent all procedures as the CXL group except UVA irradiation. The corneal properties were measured before and after the treatment in both groups by using a quantitative ultrasound method.  Changes in corneal thickness, density and stiffness were examined within each group, and the difference in the changes between the CXL group and the control group was analyzed.
Based on the measurements of the quantitative ultrasound method, the initial properties of the corneas in the CXL and the control groups were not different. After riboflavin-UVA treatment, corneal properties were altered in the CXL group. Corneal stiffness showed a statistically significant increase (2.59±0.08 GPa before crosslinking vs 2.70±0.08 GPa after crosslinking; P< 0.01). The speed of sound in corneal tissue was also increased after crosslinking (1557±23 m/s before vs. 1588±22 m/s after; P< 0.001). Corneal thickness changed from 989±79 µm to 1236±67 µm after the riboflavin-UVA procedure (P<0.01). In the control group, corneal thickness increased similarly as in the CXL group from 965±41 µm to 1159±47 µm (P<0.01). There was no significant change for both corneal stiffness (2.58±0.04 GPa vs. 2.57±0.05 GPa; P=0.50) and speed of sound (1552±13 m/s vs. 1552±17 m/s; P=0.87) in the control group. No statistically significant change was observed for corneal density in both CXL and control groups.
This study demonstrated that corneal stiffness may be increased by riboflavin-UVA-induced collagen crosslinking, and the non-invasive ultrasound technique was sensitive in detecting this change. Liu J, et al. J Biomech 2007;40:1177-1182.
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