An optical method for measuring the thickness of transparent structures has been developed, and has been used to measure, in vivo, the thickness of the human cornea. The thickness is measured by placing the anterior surface of the cornea at the focus of a beam of coherent laser light and then measuring the spacing between the interference fringes generated by the reflected light. The thickness is then calculated from the fringe spacing. The method has been used to measure corneal thickness in frog and human corneas. These measurements have been correlated with histologic and pachometer measurements of corneal thickness. A significant capability of this technique is to measure the thickness of optically opaque corneas.
Daniel G. Green, Bartley R. Frueh, and Jerrold M. Shapiro, "Corneal thickness measured by interferometry," J. Opt. Soc. Am. 65, 119-123 (1975)