Ultra-widefield High-resolution OCT angiography of Rodent Retina

In this abstract, we introduce a swpet-source optical coherence tomography (OCT) and OCT angiography (OCTA) system with a 112 field of view (FOV) to enable high-resolution peripheral retinal imaging in rat eyes. To achieve this unprecedented FOV, a contact imaging probe for rat eye was developed. This system was demonstrated on healthy adult rats, as well as oxygen induced retinopathy (OIR) rats and healthy controls with the same age. The ultrawide-field (UWF) OCT and OCTA system could allow earlier recognition of peripheral retinal disease, such as OIR, and prevent permanent vision loss. Additionally, adequate visualization of the peripheral retina has a great potential for better understanding disease mechanisms regarding the periphery. This UWF-OCT/OCTA offers significant values in clinical retinal studies and basic vision science. Purpose: To develop a ultrawide field of view (FOV) contact imaging probe for OCT and OCT angiography (OCTA) to enable high-resolution peripheral in-vivo retinal imaging in Brown Norway rat models of oxygen induced retinopathy (OIR). Methods: The system uses a vertical cavity surface-emitting laser (VCSEL) with an A-scan rate of 400 kHz. This swept-source laser has a 1060 nm central wavelength and a 100-nm bandwidth, which corresponds to an axial resolution of 3.7 µm in tissue[1]. Our sample arm contains a contact lens to increase FOV (Fig. 1). It reduces eye movement in subjects and can realize 9-µm lateral resolution with a 112 FOV in rats. We induced OIR by placing the newborn rats in an oxygen controlled chamber cycling between 50% and 10% oxygen concentration every 24 hours for 20 days[2]. Subjects were anesthetized with inhaled 2.5% isoflurane during imaging. The acquired raw spectrum data was converted to linear k-space, and compensated dispersion was applied to the split-spectrum amplitude decorrelation angiography (SSADA) algorithm to produce OCT and OCTA volumetric data[3,4]. Volumes were segmented along anatomic boundaries by an artificial intelligence algorithm to generate en face projections of specific layers[5]. Results: OIR rats and age-matched healthy controls were imaged at 27 days post-birth. OCT shows single nerve fibers. The juvenile OIR rat lacked dense microvasculature, demonstrated increased vessel tortuosity and nonperfusion area at periphery, and had lingering hyaloid vasculature relative to the age-matched healthy controls (Fig. 2). Conclusion: The ultrawide OCT and OCTA system can achieve high-resolution 112 FOV imaging in rat retina and were able to visualize vascular disparities between OIR and age-matched control.