Dependance of Stiffening on Depth in Riboflavin/UVA treated Corneas
Schilde, T., Spörl, E., Kohlhaas, M., Pillunat, L. E.
Dept. of Ophthalmology, University Hospital Carl Gustav Carus, Dresden
Purpose: Treatment of keratoconus with riboflavin/UVA is based on a significant stiffening of the cornea. The study should show until which depth the stiffening effect could be proved biomechanically.
Method: From 20 enucleated porcine eyes, 10 eyes were treated with riboflavin as photosensitizer and UVA (370 nm, 3 mW/cm2, 30 min) and 10 eyes served as controls. Two flaps of 200 mm thickness were cut with a microkeratom from each eye and strips of 5 mm width and 7 mm length were prepared. Stress-strain curves were measured with a material tester to characterize the stiffening effect.
Results: The stiffening of the first treated flaps was increased (P = 0.003) in comparison to the second treated flaps and the control flaps. Stress at 5 % strain achieved 251±160,7x103 N/m2 for the first treated flaps in comparison to 111±64,2x103 N/m2 for the first control flaps. The second treated flaps (119±68,1x103 N/m2) are 20 % stiffer than the second control flaps (99±50,1x103 N/m2) but the difference is not significant (P = 0.5). The stress of the second control flaps is smaller as the first one but the difference does not reach significance (P = 0.36).
Conclusions: Treatment of the cornea with riboflavin/UVA leads to a significant stiffening in th
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