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N. Li, S. Esquenazi, J. He, N. G. Bazan, W. Rand, H. E. P. Bazan; Comparative in vivo High-Resolution Confocal Microscopy of Corneal Epithelium, Sub-Basal Nerves and Stroma in Mice With and Without Dry Eye After PRK. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3883.
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The purpose of this study was to compare, using a new generation high-resolution in vivo confocal microscope, the epithelial morphology, sub-basal nerves and stroma in two groups of mice: one exposed to normal conditions and the other to a desiccating environment following PRK with mechanical epithelial scraping.
Twenty-two 4-8 week old female Balb/C mice were used in this study. Twenty mice underwent bilateral corneal epithelial scraping using an electric brush prior to PRK. Ten mice were placed in normal conditions (NC) and ten mice were exposed to a desiccating environment for two weeks (DE). Two mice served as controls. Corneas were analyzed in vivo using the Rostock Cornea Module of the Heidelberg Retina Tomograph (HRT-II). For all eyes, 20 confocal microscopic images of each layer, i.e., the superficial and basal corneal epithelium, anterior and posterior stroma and the endothelium were recorded. Epithelial and stromal cell densities and sub-basal and stromal nerves were measured and compared.
The density of the superficial epithelial cells was 693 ± 143 cells/ mm2 in NC and 443±128 cells/mm2 in DC (p<0.001). Basal cells, characterized as dark cells with hyper-reflective boundaries smaller than superficial cells, were significantly increased in the DE group. PRK induces the appearance of cellular bodies in the anterior stroma. Significant increase in the number of reflective structures without clearly visible nuclei was observed within the anterior and mid stroma in the DE group compared with the NC eyes. Additionally, increased nerve sprouts and higher tortuosity of sub-basal nerves were observed in the DE group. No changes in the density of endothelial cells were found in any of the two groups.
Exposure of mice to a desiccating environment after PRK with previous mechanical epithelial scraping increases epithelial turnover and higher number of reflective structures in the stroma. Additionally higher nerve beads, nerve sprouts and tortuosity of sub-basal nerves, possibly directed to repair the alterations observed at the epithelial level, was observed in the DE group.
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