Multimodal retinal imaging platform for evaluating retinal morphology in living mice

Abstract

 

Purpose

 

To evaluate the feasibility of the custom multimodal imaging platform developed at UC Davis Eye-Pod laboratory to study longitudinal changes in microscopic retinal morphology in mice in vivo.

 

Methods

 

The multimodal retinal imaging platform combining multispectral Scanning Laser Ophthalmoscopy (SLO; reflectance and fluorescence) and high acquisition speed Fourier-domain OCT was used to investigate in vivo retina structures in mice. Our imaging optics allow non-contact imaging of the mouse retina over ~50 deg FOV (~1.9 mm) as well as zoom capability, with optical lateral resolution on the order of 3 um. The SLO sub-system uses a supercontinuum light source (Fianium Ltd) within the 410-950 nm range, and three detectors, two PMTs and one spectrometer (Ocean Optics QE65000), that can be configured for different experiments with custom sets of excitation and barrier filters selected for specific intrinsic or extrinsic fluorophores in the retina. The OCT sub-system uses a high acquisition speed Fourier-domain OCT (FD-OCT) engine (125,000 A-scan/s) allowing 3D mapping of the fluorescent signals onto volumetric retinal morphology. Wild type (WT; c57Bl/6J) mice and fluorescently labeled transgenic mice were imaged with this system to evaluate its potential for longitudinal interrogation of cellular morphology and function in vivo. During the imaging, mice were anesthetized with general anesthesia with 2-3% isoflurane. Eyes were dilated and cyclopleged with Tropicamide and Phenylephrine.

 

Results

 

The system has been used to evaluate mice strains expressing various fluorescently labeled cells, including microglia, photoreceptors, mueller and ganglion cells (GCs). The figure shows representative results of a mouse expressing YFP in GCs (Thy1-YFP-H). The zoomed-in view (6x increase in the sampling density) shows that current optical lateral resolution is sufficient to visualize single cell morphology in the living animal. The fluorescence emission spectrum (insert) was measured with the SLO beam "parked" on the cell body.

 

Conclusions

 

The versatility of our multimodal retinal imaging platform enables investigation of many aspects of retinal structure and function, including the morphology in fluorescently labeled cells in living animals. We are applying these tools for non-invasive in vivo monitoring of longitudinal changes in retinal morphology and function in animal models of retinal disease.

 

 

Keywords: 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • 688 retina