Abstract
Purpose :
We have established vis-OCT fibergraphy (vis-OCTF) for visualizing and quantifying retinal ganglion cell (RGC) axon bundles in vivo. Here we further investigate whether we could track and quantify changes in the retinal nerve fiber layer (RNFL) in mice with optic nerve crush (ONC) injury.
Methods :
Optic nerve crush procedure was performed on C57BL/6 mice. Mice were imaged using vis-OCT before and 12-days after ONC. For each mouse, we acquired four vis-OCT volumes (512 A-lines × 512 B-scans) from the same eye with the optic nerve head (ONH) aligned in the four corners of the field of view. After fibergram processing, the images from each mouse were montaged to generate the final vis-OCT fibergram. The four rectangular OCT image volumes were resampled from each retina to generate a 400 μm radius circumpapillary scan centered on the ONH. After acquiring vis-OCT data at 12-days post ONC, the same retinas were immunostained for RGC axons and imaged by confocal microscopy.
Results :
We quantified the thickness of the retina and RGC axon bundle layer before and after ONC using the resampled circumpapillary B-scans. We found a significant reduction in overall retinal thickness as well as in RGC axon bundle layer thickness after ONC. We compared the vis-OCT fibergrams with their corresponding confocal images of flat-mounted retinas at 12-days post ONC. The Sholl regression coefficient (k) value, a measure for RGC axon bundle density, was consistent in vis-OCTF compared with confocal microscopy. Following ONC injury, the vis-OCTF k values increased for three mice that we have monitored, which corresponded to a higher slope in the Sholl regression plot. Our results indicate a faster change in RGC axon bundle density moving away from the ONH. We further quantified the axon bundle width for all five mice, and a 25% reduction in RGC axon bundle width was observed at 12 days after ONC.
Conclusions :
Out results show that vis-OCTF can be used to evaluate RNFL damage in vivo in mice with optic neuropathy. The quantifications of lateral RGC axon bundle thickness and density could provide more detailed information for better diagnosis at the earlier stages of optic neuropathies.
This is a 2021 ARVO Annual Meeting abstract.