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Riccardo Vinciguerra, Eberhard Spoerl, Mario R. Romano, Pietro Rosetta, Paolo Vinciguerra; Comparative Stress Strain Measurements Of Human Corneas After Transepithelial UV-A Induced Cross-linking: Impregnation With Iontophoresis, Different Riboflavin Solutions And Irradiance Power. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1518. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To compare the change in biomechanical properties of human cadaver corneas after standard transepithelial cross-linking (CXL-TE) versus CXL-TE using iontophoresis, different solutions and UV-A power.
Twelve human cadaver corneas were divided in 4 different groups according to methods of impregnations and UV-A power used: Group A (three corneas, treated with CXL-TE using an irradiance power of 3 mW/cm2 for 30 minutes and riboflavin solution with 15 % dextrane and Tromethamine); Group B (three corneas treated with CXL-TE using an irradiance power of 3 mW/cm2 for 30 minutes and riboflavin solution with Tromethamine); Group C (three corneas treated with CXL-TE using an irradiance power of 10 mW/cm2 for 10 minutes and riboflavin solution with Tromethamine); Group D (three corneas treated with an irradiance power of 10 mW/cm2 for 10 minutes, the impregnation was obtained with the aid of iontophoresis and a riboflavin solution with Tromethamine). After cross- linking, static stress-strain measurements of the corneas were performed using a microcomputer-controlled biomaterial tester with a pre-stress of 5x103 Pa. Stress stain curves were fitted with an exponential function and the Young's modulus was calculated. Thickness of the cornea was measured with an ultrasound pachymeter.
Stress strain measurement showed an increase in corneal rigidity after cross-linking compared to standard CXL-TE, indicated by a rise in strain and in Young’s modulus calculated at 10% strain. Considering group A as standard of comparison, group B showed an increase by a factor of 1.45, group C by a factor of 1.26, group D by a factor of 1.81. Mean corneal thickness was: 627 µm for group A, 628 µm for group B, 527 µm for group C, 665 µm for group D.
CXL-TE is able to increase mechanical rigidity in human corneas in selected groups. Stress strain results showed a maximal effect in the iontophoresis group, probably due to the increased riboflavin concentration in the stroma. Stress strain measurement in the other groups showed a better results using riboflavin solution without dextrane and 3 mW/cm2 of irradiance power.
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