The human limbus. A scanning electron microscopic study.

Fourteen human limbal biopsy specimens were obtained from seven normal subjects. The epithelial surface was examined by scanning electron microscopy. Epithelial cell surfaces varied greatly in shape and size, and mosaics of three- to six-sided irregular polygons were formed. Microvillar borders of cells were distinct. Cell sizes ranged from 3 to 20 micron across. Light and dark cells were present and randomly distributed. A few cells were covered with microplicae; the remainder of the cells were covered with microvilli. Intercellular crypt openings measuring 1 to 10 micron in diameter were distributed randomly over all specimens. These openings were believed to be related to goblet cells. Many openings were plugged with what appeared to be mucus. Many surface-level intercellular structures were present; they corresponded in diameter to the surface openings. The human limbal epithelium varies from both the upper tarsal conjunctiva and the cornea.