Rapid acquisition of a three-dimensional image of corneal nerve distribution and its various parameters

Objective

To investigate a rapid protocol for the acquisition of a three-dimensional (3D) image of corneal nerve distribution and its various parameters.

Methods

Four SPF female C57BL/6 mice were selected and four corneal samples with complete limbi were obtained using a dissecting microscope after the sacrifice of mice euthanized by ether.After conventional fixation, permeabilization, and immunostaining by an anti-β-Ⅲ tubulin fluorescent-conjugated antibody, a whole-nerve image of the whole-mount cornea was captured under a 60X oil lens using a scientific complementary metal-oxide-semiconductor detector and a high-resolution deconvolution microscope.The 3D image of the corneal nerve fiber was obtained after 3D deconvolution processing, Z-axis data projection, and automatic stitching using the self-contained image processing software of the microscope system.The corneal nerve density in different areas was analyzed using the automatic detection mode in the Filament Tracer module and the manual Autopath module of the interactive microscopic image analysis software Imaris.The use and care of animals complied with the statement of the Association for Research in Visual and Ophthalmology, and the study protocol was approved by an Experimental Animal Welfare Committee of Jinan University (No.JN-A-2002-01).

Results

It was found that stromal nerve fibers in a dense network entered the Bowman membrane near the limbus, and branches of stromal nerve fibers formed subbasal nerve plexus, which stretched toward the center of the cornea to form a dense neural network-like structure and converged into a vortex-like structure at the apex of the cornea.Some subbasal nerves entered the epithelial layer vertically and some branches of nerve endings were found.Through the automatic detection mode of Imaris software, a gradual increase of the density from (2 488.88±282.84)μm/μm² at the limbus to (5 766.66±298.55)μm/μm² at the center of the cornea of the subbasal nerve branches, and a decrease of the density from (40.99±0.99)μm/μm² at the limbus to (34.57±1.28)μm/μm² at the center of the stromal nerves were found.It was also found that the stromal nerves at the limbus entered the Bowman membrane for about 151 μm and then began to branch to form subbasal nerves.

Conclusions

The high-resolution deconvolution microscope system can be used to study the 3D distribution of the whole corneal nerve.Additionally, Imaris can be used for obtaining various parameters of the corneal nerves automatically and quickly.

Cornea; Nerve fibers; Imaging, three-dimensional; Image processing, computer-assisted; Deconvolution