Alignment of Visible-Light Optical Coherence Tomography Fibergrams with Confocal Images of the Same Mouse Retina

The present protocol outlines the steps for aligning in vivo visible-light optical coherence tomography fibergraphy (vis-OCTF) images with ex vivo confocal images of the same mouse retina for the purpose of verifying the observed retinal ganglion cell axon bundle morphology in the in vivo images.

In recent years, in vivo retinal imaging, which provides non-invasive, real-time, and longitudinal information about biological systems and processes, has been increasingly applied to obtain an objective assessment of neural damage in eye diseases. Ex vivo confocal imaging of the same retina is often necessary to validate the in vivo findings especially in animal research. In this study, we demonstrated a method for aligning an ex vivo confocal image of the mouse retina with its in vivo images. A new clinical-ready imaging technology called visible light optical coherence tomography fibergraphy (vis-OCTF) was applied to acquire in vivo images of the mouse retina. We then performed the confocal imaging of the same retina as the "gold standard" to validate the in vivo vis-OCTF images. This study not only enables further investigation of the molecular and cellular mechanisms but also establishes a foundation for a sensitive and objective evaluation of neural damage in vivo.

Retinal ganglion cells (RGCs) play a critical role in visual information processing, receiving synaptic inputs through their dendritic trees in the inner plexiform layer (IPL) and transmitting the information via their axons in the retinal nerve fiber layer (RNFL) to the brain^1,2,3,4. In diseased conditions such as glaucoma, early RGC degeneration may result in subtle changes in the RNFL, the ganglion cell layer (GCL), the IPL, and the optic nerve in both patients and rodent models^5,

All animal procedures were approved by the Institutional Animal Care and Use Committee at the University of Virginia and conformed to the guideline on Use of Animals from the National Institute of Health (NIH). See the Table of Materials for details related to all materials, reagents, and instruments used in this protocol.

1. In vivo vis-OCT imaging

1. The vis-OCT system
   1. Image the mice eyes using a small animal vis-OCT system that.......

The composite vis-OCT fibergram is compared with the corresponding confocal image of flat-mounted retina immunostained with Tuj-1 for RGC axons (Figure 1D, top panel). Axon bundles imaged by vis-OCTF can be matched with the Tu-j1-labeled axon bundles on the confocal image. Blood vessels usually exhibit distinguishable branching structures compared with surrounding axon bundles in fibergram images, which can be matched with the ICAM-2-labeled blood vessels on the confocal image (

There are two steps in this protocol that require attention. First, it is necessary to ensure that the animal is under deep anesthesia and that their eyes are fully dilated before vis-OCT imaging. If the mice are not adequately anesthetized, their fast breathing may lead to unstable movements of the en face images, which can adversely affect the quality of the fibergram. Moreover, insufficient dilation can also have a negative impact on image quality since the iris may obstruct the light, preventing it from reac.......

This study is supported by the Glaucoma Research Foundation Shaffer Grant, 4-CA Cavalier Collaborative Award, R01EY029121, R01EY035088, and Knights Templar Eye Foundation.