In-vivo slit scanning confocal microscopy of normal corneas in Indian eyes

To study the cellular populations of healthy corneas of Indian eyes using confocal microscopy and to evaluate the correlation with age, gender and laterality.

The central corneas of 100 eyes of 50 healthy subjects were examined using an in-vivo slit scanning confocal microscope (Confoscan 2). Images were analysed for cell densities of the epithelium, stroma and endothelium.

Good quality images enabling analysis of all cell layer populations were obtained in 74 eyes of 43 healthy subjects (22 males and 21 females) with a mean age of 31.89 +/- 13.47 (range 19-71 years). The basal epithelial cell density was 3601.38 +/- 408.19 cells/mm2 (range 3017.3-4231.1 cells/mm2). The mean keratocyte nuclei density in the anterior stroma was 1005.02 +/- 396.86 cells/mm2 (range 571.6-1249.6 cells/mm2) and in the posterior stroma was 654.32 +/- 147.09 cells/mm2 (range 402.6-1049.1 cells/mm2). Posterior keratocyte nuclei density was 30.76% less than the anterior stromal keratocyte nuclei density. The difference in keratocyte nuclei density was statistically significant (P=0.001). The mean endothelial cell density was 2818.1 +/- 361.03 cells/mm2 (range 2118.9-4434 cells/mm2) and the mean endothelial cell area was found to be 385.44 +/- 42.66 mm2 (range 268.9-489.2 mm2). Hexagonal cells formed 22.5-69.4% of the endothelial cell populations (mean 42.04 +/- 11.81%). Mean coefficient of cell size variation was 32.29 +/- 3.06 (range 27.2-39.2). No statistically significant differences were found in cell densities of any corneal layer either between female and male patients or between right and left eyes. Basal epithelial cell density, anterior stromal keratocyte nuclei and posterior stromal keratocyte nuclei density were unaffected by age (r=0.12, 0.07, -0.12 respectively) (P=0.001). There was a statistically significant negative correlation between mean endothelial cell density and increase in age (r=-0.42, P=0.001). Coefficient of cell size variation and age were positively correlated (r=0.73, P=0.001).

In-vivo slit scanning confocal microscopy is useful for the study of corneal cell populations. Our study provides normative data of these cell populations.