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R Glenn Hepfer, Peng Chen, George O Waring, Hai Yao; Anisotropic Diffusion in the Corneal Stroma Measured by Three-Dimensional Fluorescence Recovery After Photobleaching. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2372.
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© 2017 Association for Research in Vision and Ophthalmology.
This study investigates transport properties within the corneal stroma. The corneal stroma is a highly organized tissue, with collagen fibers that run primarily in the lateral direction. Such organization may give rise to anisotropic diffusion, i.e. diffusion that is dependent on direction. We hypothesize that anisotropic diffusion can be detected in the corneal tissue of whole ex-vivo eyes through three-dimensional fluorescence recovery after photobleaching (3D FRAP).
Fresh, intact porcine eyes were obtained from a local slaughterhouse. The epithelia of the eyes were removed, and a solution containing a fluorescent probe was applied to the cornea. 3D FRAP was performed on the corneas and a custom Matlab program was used to calculate the diffusion coefficient in three directions: nasal-temporal (X), superior-inferior (Y) and anterior-posterior (Z). 3D FRAP was also performed on glutaraldehyde-treated corneas.
The diffusion coefficient in the Z direction was significantly decreased when compared to the diffusion coefficients in the X (P=0.004, ANOVA) and Y (P<0.0001, ANOVA) directions. There was no significant difference between the diffusion coefficients in the X and Y directions. The corneas treated with glutaraldehyde had significantly reduced diffusion coefficients in all directions when compared to normal corneas (P<0.0001, ANOVA). Furthermore, there was no significant difference between diffusion coefficients in different directions in the glutaraldehyde-treated corneas.
Native porcine corneas exhibit anisotropic diffusion; the diffusion in directions parallel to collagen fibers is faster than the diffusion in directions orthogonal to collagen fibers. The glutaraldehyde treatment decreases the diffusion in the cornea and eliminates the anisotropy. The technique presented will be useful in examining the effects of certain corneal treatments (e.g. corneal cross-linking) as well as in developing tissue-engineered corneas that mimic the material properties of the native tissue.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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