Dimensions and morphology of the cornea in three strains of mice

To use a histologic approach to obtain dimensional and morphologic information on the cornea in three commonly used strains of mice.

Adult mice (three each of 129/SVJ, C57BL/6, and BALB/c) were euthanatized, and the eyes were enucleated, immersed in 2% glutaraldehyde fixative, and prepared for light and transmission electron microscopy. The full corneal, epithelial, stromal, and posterior limiting lamina (PLL) with endothelium thicknesses were measured at the same location centrally and peripherally.

All three strains showed a statistically significant (P < 0.001) decrease in overall thickness in the peripheral compared with the central cornea. The decrease was due to a reduced thickness of both the epithelium and the stroma. The stroma and epithelium contributed to approximately two thirds and one third of the total corneal thickness, respectively. The epithelium had the classic stratified layout and consisted of 13.00 +/- 1.41 layers centrally versus 10.33 +/- 1.37 peripherally. Some adaptation of stromal tissue was found immediately adjacent to the epithelial basement membrane, but a clearly defined anterior limiting lamina did not exist. The stroma was organized into lamellae but lacked the anterior branching and interweaving reported in humans and had unmyelinated nerve fibers within micrometers of the endothelium. The PLL was 2.17 +/- 0.3 microm thick and was divided into pre- and postnatal layers, with striated bodies in the postnatal portion.

This study demonstrated that in the three strains of mice examined, the cornea becomes significantly thinner toward the periphery. Dimensionally, proportionally, and anatomically the three strains used appeared to be similar. However, morphologic differences were observed compared with other mammals, and awareness of these differences is important when using the mouse as an animal model applicable to the human.