Retinitis pigmentosa (RP) is a group of inherited diseases marked by progressive photoreceptor degeneration, affecting 1.5 million people worldwide. The vascular (choroidal and retinal) layers located on either side of the retina and other (bipolar and ganglion) cell layers are also affected. Current clinical assessment of RP relies heavily on visual testing. Non-invasive imaging technologies capable of detecting layer-specific cellular and vascular changes would enable objective early detection, longitudinal disease staging, monitoring of therapeutic intervention, and improved understanding of the underlying pathophysiology. Optical-based retinal imaging techniques can be limited by media opacity (i.e., cataracts and vitreous hemorrhages) which precludes visualization of deep retinal layers and vessels. In contrast, magnetic resonance imaging (MRI) provides non-invasive images of anatomy, physiology and function without depth limitation. Achieving sufficient spatial resolution for retinal MRI, however, remains challenging. In this proposal, we will develop novel anatomical, physiologic and functional MRI to resolve various layers of the retina at 60x60x500 5m, and vigorously test this capability by longitudinally investigating progressive, layer-specific retinal degeneration in the Royal-College-of-Surgeon (RCS) rat retinas, an established model of human RP.
This proposal outlines the development, cross-validation and application of novel MRI approaches to resolve structural, physiological and functional laminar specificity of the retina at very high spatial resolution. It has strong clinical significance and potential impact to the field in that it can provide 1) an early marker of retinal degeneration and for monitoring therapeutic intervention and 2) powerful insights into how retinal and choroidal blood flow and oxygenation are regulated and how retinal degeneration affects the two vasculatures and the neural tissues they subserve. Data from these animal studies should advance these areas of research, open up new avenues for retinal research, and lay the foundation for future human studies.
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