SCANNING SLIT CONFOCAL MICROSCOPIC OBSERVATION OF CELL MORPHOLOGY ANDMOVEMENT WITHIN THE NORMAL HUMAN ANTERIOR CORNEA

Purpose: Noninvasive in vivo observations of the anterior human cornea were performed to study cell structure and dynamics. Cellular element s were identified by their location, morphology, and pattern of moveme nt. The hypothesis that cells in the epithelial layer of the normal co rnea migrate centripetally was tested. Methods: Using a scanning slit confocal microscope with a new 0.75-numeric aperture contact objective , individual cells of normal human corneas were observed over time, qu antifying the velocity and direction of cellular movement within the b asal epithelial layer. Results: Basal epithelial cells, wing cells, th e basal epithelial nerve plexus, and the subepithelial nerve plexus we re identified readily. Centripetal motion was observed for three corne al cell types: basal epithelial cells, basal epithelial nerves, and un identified cellular elements (possibly Langerhans cells). The unidenti fied cellular elements moved along the length of the basal epithelial nerves. The basal epithelial nerve plexus maintained a roughly stable topology as it slid centripetally. New nerve material appeared at the site of entry of the nerve into the epithelium. No growth cones were p resent at the distal termini of the growing epithelial nerves. Conclus ion: In the midperiphery of the normal human cornea, basal epithelial cells and nerves slide centripetally, probably in concert. Unidentifie d cellular elements used the basal epithelial nerve plexus as a pathwa y for intraepithelial movement. Observations in this study suggest tha t neurite growth occurred by the addition of new membrane material alo ng the length of the axon rather than at a distal growth cone.