[In vivo study of normal human limbal and central corneas using laser confocal microscope]

To observe the microstructure and cellular populations of normal human limbal and central corneas using laser confocal microscope.

The study was consisted of 28 eyes of 15 examiners (age distribution, 16-61 years). After examinations with slit lamp biomicroscopy and ophthalmoscope, the images of superior, inferior limbus and central cornea were acquired by laser confocal microscope. Corneal microstructure and cell morphology were analyzed, and cell densities were measured.

Lateral (x, y axis) and axial (z axis) images of limbal and central cornea were clear and vivid. Limbal palisades of Vogt were visible at the superior and inferior limbus. The red blood cells in the vessel of limbus were visible. The arrangement of surface epitheliums was rather loose, with bright borders and dark cell bodies. The surface epithelial cell density was (812 +/- 297) cells/mm(2) at the superior limbus and (785 +/- 263) cells/mm(2) at the inferior limbus. There was no statistical difference between the two group (P > 0.05). The bright and dendriform Langerhans cells were readily visible just under the epithelial cells. The Langerhans cell density was (288 +/- 102) cells/mm(2) at the superior limbus and (254 +/- 127) cells/mm(2) at the inferior limbus. There was no statistical difference between the two group (P > 0.05). At central cornea, the surface epithelial cells were loose, the borders of the cell were clear and bright, and the cell bodies were dark. The cell density was (1098 +/- 315) cells/mm(2), there were more cells in central cornea than other area of superior and inferior limbus (P < 0.05). The arrangement of basal epithelial cells was tight. Nerve plexus at subepithelium and anterior stroma were prominent with strong brightness. Langerhans cells were occasionally visible, and cell density cannot be measured. Subepithelial nerve fibers were thin with high tortuosity and a lot of branches, and deeper ones were thick with low tortuosity and few branch. In the stroma, separated keratocytes were visible under dark background, the boundaries were vague, the nucleis were bright and spindly. Hexagonal endothelial cells were arranged in order with light cell bodies and dark borders. The thickness of whole cornea, stroma or epithelium was (543.0 +/- 62.9), (462.0 +/- 69.5), (59.9 +/- 11.2) microm respectively.

Laser confocal microscopy provides non-invasive, real-time, in vivo images of limbal and central corneas characterized with refined image definition, exact depth localization. It is valuable for basic research and clinical diagnosis of corneal disease.