The measurement of corneal thickness from center to limbus in vivo in C57BL/6 and BALB/c mice using two-photon imaging

Abstract

The mouse corneal thickness is very important for research into the fields of eye disease. However, the in vivo corneal thickness for the entire cornea from the pupil to the limbus was not determined. We measured in vivo corneal layer thicknesses in different corneal areas, from the central cornea to the limbus, in the widely used inbred C57BL/6 and BALB/c mouse strains using two-photon (2 PH) imaging. Eight corneas of the C57BL/6 or BALB/c were scanned using a 2 PH laser scanning fluorescence microscopy system. A total of 14 thicknesses of the different corneal layers, from different corneal regions, were measured using image processing software. In both C57BL/6 and BALB/c mice, the thickness of the corneal layers was inhomogeneous in different areas of the cornea, and all of the layers had their minimum thickness at the limbus. In C57BL/6 mice, the thickness of the corneal layers gradually increased from the central to the paracentral cornea, peaked at the fifth measurement point in the paracentral area, and decreased from this point to the limbus. In BALB/c mice, the thickness of the entire cornea and corneal epithelium had its maximum at the central cornea and gradually decreased from the central cornea to the peripheral cornea and to the limbus. The thickness of the corneal stroma and endothelium had its maximum at the fourth measurement point in the paracentral cornea and gradually decreased from the paracentral cornea to the limbus. The ratio of epithelial thickness to the total corneal thickness gradually decreased from the central cornea to the limbus in both C57BL/6 and BALB/c mice. The minimum ratio was observed at the fourteenth measurement point in both C57BL/6 and BALB/c mice. The ratio of stromal and endothelial to the total corneal thickness gradually increased from the central cornea to the limbus in both C57BL/6 and BALB/c mice. The maximum ratio was observed at the fourteenth measurement point in C57BL/6 mice. The ratio at the first eight measurement points was significantly lower in BALB/c than in C57BL/6 mice (P < 0.05). Our study demonstrated that the thickness of the entire cornea, the corneal epithelium, the corneal stroma and the endothelium was inhomogeneous in different areas of the cornea. Moreover, all of the layers exhibited a minimum thickness at the limbus in both C57BL/6 and BALB/c mice. Furthermore, the corneal thickness in different areas varied between C57BL/6 and BALB/c mice, and the variation in thickness with respect to corneal location for these strains was dissimilar. When using the mouse as an animal model to examine the cornea, it is important to note the differences between humans and mice.