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J. Dias, N. M. Ziebarth, M. Prabakar, L. Lau, C. Rowaan, V. T. Moy, S. H. Yoo, J.-M. A. Parel; Elasticity of Corneas Treated With UVA and Riboflavin Assessed by Atomic Force Microscopy. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4634.
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© ARVO (1962-2015); The Authors (2016-present)
To measure the elasticity of human cadaver corneas after crosslinking treatment with ultraviolet light and riboflavin using atomic force microscopy (AFM).
Four pairs of human cadaver eyes (age: 54-86 years, <8 days postmortem) were used for this study: the right eye was treated and the left eye served as the control. The corneal thickness was restored to physiological levels by placing the whole globe, cornea side down, in 25% Dextran for 24 hours. The epithelium was removed for all eyes using alcohol and a cotton swap. One drop of 0.1% riboflavin solution (10mg riboflavin-5-phosphate in 10mL Dextran 20% solution) was placed on the cornea of the right eye every 5 minutes for 30 minutes. The cornea was then irradiated for 30 minutes using UVA light (=378nm) with an irradiance of 3mW/cm2. During irradiation, one drop of the riboflavin solution was placed on the cornea every 5 minutes. The cornea was removed from the treated and untreated eyes. Elasticity was measured with a custom-built laboratory AFM designed for mechanical testing of ophthalmic tissues. The anterior corneal surface was probed with an AFM cantilever tip. Young’s modulus was calculated using the Sneddon model for a conical indenter.
Young’s modulus of the untreated cornea ranged from 4.9kPa to 29.1kPa; Young’s modulus of the treated cornea ranged from 10.5kPa to 74.5kPa. A t-test comparing contralateral eyes (treated and untreated) demonstrated a significant difference in all samples (p<<0.001).
Treatment with ultraviolet light and riboflavin results in a significant increase in corneal stiffness. AFM measures rigidity without corneal damage, enabling histology analysis (eSEM).Support: IMSD (JD); Florida Lions Eye Bank; NIH center grant P30-EY014801; Research to Prevent Blindness; NSF-BITC (VM); NIH GM55611(VM); Scientific Advisory Committee, University of Miami; Henri and Flore Lesieur Foundation (JMP).
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