Laser scanning in vivo confocal microscopy of the normal human corneoscleral limbus

PURPOSE. To elucidate the structure of the human corneoscleral limbus by in vivo laser scanning confocal microscopy and to correlate limbal epithelial dimensions and density with the central epithelium and in relation to age. METHODS. Fifty adult subjects were recruited into one of two age groups: younger (age < 45 years) and older (age >= 45 years). Fifty left eyes of these 50 healthy subjects were examined by laser scanning in vivo confocal microscopy, to assess the basal epithelium of the central cornea and inferior limbus. Mean epithelial cell diameter, area, and density were calculated for the central basal epithelium, limbus-corneal basal epithelium, and limbus-palisade epithelium. RESULTS. Data were analyzed in relation to the two age groups, group A, 30 +/- 6 years (n = 25; mean +/- SD), and group B, 60 +/- 11 years (n = 25; P < 0.01). Mean epithelial density in the limbus-cornea and limbus-palisade regions decreased significantly with age: limbus-cornea group A = 7253 +/- 1077 cells/mm(2) group B = 6614 +/- 987 cells/mm(2), P = 0.03; limbus palisade group A = 5409 +/- 799 cells/mm(2), group B = 5055 +/- 722 cells/mm(2), P = 0.03). Central corneal epithelial density did not change with age: group A = 6162 +/- 503 cells/mm(2), group B = 6362 +/- 614 cells/mm(2), P = 0.08. Mean epithelial density was greatest at the limbus-cornea (7010 +/- 1081 cells/mm(2)) and lowest at the limbus-palisades (5289 +/- 847 cells/mm(2)). The mean width of palisade ridges was 25.0 +/- 6.3 mu m. CONCLUSIONS. This is the first study to image clearly the living human corneal limbus by laser scanning in vivo confocal microscopy and to demonstrate quantitative changes in the basal epithelium with age.