Panretinal high-resolution OCT angiography for rodent imaging

Abstract

Purpose : To develop a high-speed, high-resolution, ultra-wide field of view (FOV) OCT and OCT angiography (OCTA) to enable in vivo panretinal imaging in rodents.

Methods : The system uses a vertical cavity surface-emitting laser (VCSEL) (Thorlabs, Inc., USA) with an A-scan rate of 500 kHz. It outputs at a center wavelength of 1064 nm with a 103 nm usable optical bandwidth. A high-focus power contact lens (CL in Fig.1, Quad Pediatric, Volk Optical Inc., USA) is employed to maximize the incident beam directed onto the rodent's cornea. Together with the lens groups L1 and L2, they compose a 4.7× telescope of an asymmetrical optical formula that effectively overcomes the constraints inherent in rodent retinal wide-field imaging that a common 4f setup has not achieved. The theoretical maximum imaging FOV is 112°, and the lateral resolution is 8.9 µm on rat's retina.

Results : We imaged a healthy Brown Norway adult rat with our system (Fig. 2). We were able to image individual nerve fibers (Fig.2(b) and (c)), and capillaries network (Fig. 2(e) and (f)) in the whole 112° FOV across multiple layers.

Conclusions : We have successfully developed a novel high-resolution ultra-wide FOV OCTA system for rodent panretinal imaging, with a high-performance asymmetrical optics design offering a maximum 112 degrees visual angle, and a lateral resolution of 8.9 µm. We were able to visualize layer-specific structural and vascular image of high quality.

This abstract was presented at the 2024 ARVO Imaging in the Eye Conference, held in Seattle, WA, May 4, 2024.

 

System design. (a) Schematic diagram and photo of the OCTA system. (b) Side view of 3D layout of the imaging probe in OpticsStudio, with colored beams corresponding to different scanning angles in the orthogonal X and Y directions.

 

112 degrees high resolution en face retina images of a healthy Brown Norway rat. (a) Structural OCT projection of the whole retina, exemplifying the large FOV that can be achieved with our system. (b) Structural OCT projection of the nerve fiber layer. (c) Cropped images from the highlighted region in (b), with clear differentiation of individual nerve fibers, demonstrating the high lateral resolution achieved by the system. (d) OCTA projection of the superficial vascular layer. (e) OCTA projection of the deep vascular layer. (f) Cropped images from the highlighted region in (e), showing detailed capillaries with lobular nature.