On the Evaluation of the Corneal Epithelial Surface by Scanning Electron Microscopy

A comprehensive and objective survey is presented of the use of the scanning electron microscope from 1967 to 1989 to assess the characteristics of the corneal epithelial surface in the rabbit and other vertebrates. The technique shows the corneal surface as a mosaic of cells that are very heterogeneous with respect to character (light, medium, and dark electron reflexes), size (small, medium, and large), and shape (angular or rounded), yet the numerous published micrographs of normal corneas show substantial differences. The reasons for these differences are discussed using examples of 50 to 15,000 x magnification micrographs of rabbit corneas within the context of the basic principles of glutaraldehyde-based fixation of biological tissues for electron microscopy. The qualitative similarities between the scanning electron microscope image and the in vivo reflected light microscope (specular microscopy and CONFOCAL microscopy) image are reviewed and discussed.