In vivo confocal microscopic evaluation of Langerhans cell density and distribution in the corneal epithelium of healthy volunteers and contact lens wearers

Purpose: To examine and compare the density and distribution of Langerhans cells (LCs) in the corneal epithelium of healthy volunteers and contact lens wearers. Methods: A total of 225 eyes of 130 healthy volunteers (age, 17-81 years) without history of ocular inflammation, trauma, or surgery and 98 eyes of 55 contact lens wearers (age, 13-76 years) were examined in vivo with the combination of the Heidelberg Retina Tomograph II and in-house-invented Rostock Cornea Module. Results: In healthy volunteers, in vivo confocal microscopy revealed LCs in 31% of all volunteers, with 37 of these 43 volunteers presenting LCs both in the center and the periphery of the cornea with densities of 34 +/- 3 and 98 +/- 8 cells/mm(2), respectively. In the group of contact lens wearers, 55% of all corneas presented with LCs, and 11 of these 33 corneas revealed LCs at central and peripheral locations. Although LC densities were markedly higher in both the central (78 +/- 25 cells/mm(2)) and the peripheral cornea (210 +/- 24 cells/mm(2)) of contact lens wearers, the gradient of LC density from peripheral to central cornea was found almost identical in both groups. In the central cornea, LC density decreased with duration of contact lens wear. LCs were located at the depth of 35 to 60 p,m (ie, the level of lower intermediate cells, basal cells, and subepithelial nervous plexus). LCs presented as either large cells bearing long processes or smaller cells lacking cell dendrites, most supposedly indicating mature and immature phenotype, respectively. Conclusions: In vivo confocal microscopy enables evaluation of LC density and distribution in corneal epithelium. LCs were found present both in the center and the periphery of the cornea without difference in distribution between healthy volunteers and contact lens wearers. However, contact lens wearers revealed almost twofold higher LC densities in both locations, implying chronic mechanical irritation of the cornea in response to the contact lens as foreign body. Taken together, analysis of LC using in vivo confocal microscopy provides helpful information for a better understanding of contact lens-disturbed ocular homeostasis.