The Effect of Age on the Density and Orientation of Subbasal Nerves in the Normal Human Cornea

Abstract

Abstract: : Purpose: To measure subbasal nerve density and orientation in normal human corneas across a broad age range. Methods: Sixty–five normal corneas of 65 subjects were examined by using tandem scanning confocal microscopy. Ages of subjects ranged from 15 to 79 years, with 5 subjects from each hemidecade. Subbasal nerve fiber bundles appeared as bright, well–defined linear structures in confocal images of the central cornea. Images in 3 to 8 scans per eye were randomly presented to a masked observer. The mean subbasal nerve density (total nerve length within a confocal image [image area= 0.166 mm²]) and the mean nerve orientation were determined by using a custom software program. Correlations between age and subbasal nerve density and subbasal nerve orientation were assessed using Pearson correlation coefficients. Results: The subbasal nerve plexus was visible in the central cornea of all subjects (35 men, 30 women). The mean central subbasal nerve density was 8,404 ± 2,012 um/mm² (range, 3,735 to 14,018 um/mm²). The mean subbasal nerve orientation was 94 ± 16° (range, 42° to 146°). We found no correlation between age and subbasal nerve density (r=0.21, P=0.09, n=65) or subbasal nerve orientation (r=–0.19, P=0.12, n=65). Conclusions: The density and orientation of the human corneal subbasal nerve plexus does not change with age.

Keywords: anatomy • microscopy: confocal/tunneling • cornea: basic science