Abstract
Purpose::
The mouse has become a widely utilized experimental model in many areas of ophthalmic research. The purpose of this study is to provide dimensional information on the mouse cornea and to determine similarities between 129/SVJ and C57BL/6 mice.
Methods::
Seven 129/SVJ mice total (three wild type, four heterozygous for Cnlp), and four C57BL/6 mice (2 juvenile, 2 adult) were euthanized. The eyes were enucleated and immersed in glutaraldehyde fixative, 2 % or 2.5 % respectively. Corneas were processed using an established corneal tissue processing protocol. Thick sections were stained with 1 % toluidine blue and viewed at 200X with an Olympus BX51 light microscope. The full corneal, epithelial, stromal and posterior limiting lamina (PLL) with endothelium thicknesses were measured from a single section, three times each at the same location, centrally and peripherally. Peripheral measurements were taken at the extremity of the cornea, defined histologically as immediately central to limbal loops and central to the anterior edge of the trabecular meshes. Central measurements were taken between 880-1150 um from the peripheral measurement. Measurements were taken using NIH Image 1.63.
Results::
Both C57BL/6 and 129/SVJ mice showed a statistically significant difference between the central corneal thicknesses and the periphery. Average central thickness for the 129/SVJ mouse was 122.55 ± 8.51 um, versus 75.10 ± 10.77 um in the periphery. The C57BL/6 mouse showed a significant difference in overall thickness depending on age of the mouse. The juvenile and the adult measured an average of 110.69 um and 167.01 um respectively centrally, versus 87.62 um and 120.87 um in the periphery. Decreased overall thickness was due to reduced thickness in the epithelium and stroma towards the periphery. In both strains of mice the epithelium contributes to approximately 1/3 of the total corneal thickness with the stroma accounting for approximately 2/3.
Conclusions::
The study demonstrates that in the wild type, heterozygote 129/SVJ and in the C57BL/6 mouse the cornea becomes thinner towards the periphery. The mouse cornea was found to be shaped as a positive powered meniscus lens. In contrast the human cornea is shaped as a negative powered meniscus lens with the center being thinner than the periphery.
Keywords: cornea: basic science • anatomy