Age-related differences in the normal human cornea: a laser scanning in vivo confocal microscopy study

Aims: To quantify and establish baseline normative data for age-related differences in cellular and innervation density in the normal, healthy, human cornea using laser scanning in vivo confocal microscopy. Methods: Cross-sectional study of 85 normal subjects assessed via corneal topography and laser scanning in vivo confocal microscopy. Results: Mean age was 38-16 years (range 18-87 years) and 60% of subjects were female. Anterior keratocyte density declined by 0.9% per year (r = -0.423, p < 0.001), posterior keratocyte density declined by 0.3% per year (r= -0.250, p = 0.021) and endothelial cell density declined by 0.5% per year (r= -0.615, p < 0.001). Sub-basal nerve fibre density declined by 0.9% per year (r= -0.423, p < 0.001). No association was observed between age and basal epithelial cell density, or between age and central corneal thickness, corneal astigmatism or horizontal corneal diameter (p < 0.05). No association was observed between subject gender and corneal cell or innervation density. Conclusions: Using laser scanning in vivo confocal microscopy this study highlights a significant, and relatively linear, reduction in keratocyte and endothelial cell density with increasing subject age. Interestingly, corneal sub-basal nerve fibre density also significantly decreases with increasing age. In vivo laser scanning confocal microscopy provides a safe, non-invasive method for the establishment of normative data and assessment of alterations in human corneal microstructure following surgery or disease processes.