Measurement of the anisotropic thermal conductivity of the porcine cornea

- The thermal conductivity of porcine cornea = 0.53 W m−1 K−1 at normal hydration.
- The thermal conductivity of porcine cornea has 14% anisotropy at normal hydration.
- The perpendicular thermal conductivity of porcine, human, & feline samples were equal.
- Including anisotropy may improve the accuracy of models of heating in the cornea.
- Measured conductivity values differed by 3% from the two-layer models of Poppendiek.

Accurate thermal models for the cornea of the eye support the development of thermal techniques for reshaping the cornea and other scientific purposes. Heat transfer in the cornea must be quantified accurately so that a thermal treatment does not destroy the endothelial layer, which cannot regenerate, and yet is responsible for maintaining corneal transparency. We developed a custom apparatus to measure the thermal conductivity of ex vivo porcine corneas perpendicular to the surface and applied a commercial apparatus to measure thermal conductivity parallel to the surface. We found that corneal thermal conductivity is 14% anisotropic at the normal state of corneal hydration. Small numbers of ex vivo feline and human corneas had a thermal conductivity perpendicular to the surface that was indistinguishable from the porcine corneas. Aqueous humor from ex vivo porcine, feline, and human eyes had a thermal conductivity nearly equal to that of water. Including the anisotropy of corneal thermal conductivity will improve the predictive power of thermal models of the eye.