Noninvasive Imaging of Chorioretinal Oxygen Tension

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DESCRIPTION (provided by applicant): The metabolic function of the retinal cells is based on the availability of nutrients and oxygen that are supplied by the chorioretinal circulations. Retinal hypoxia is implicated in the development of major and common blinding human eye diseases, such as, diabetic retinopathy and age-related macular degeneration. However, the relative contribution of the choroidal and retinal vasculatures to the retinal oxygenation in health and disease has not been adequately studied. Moreover, the role of oxygen in the development of retinal diseases, and their associated vascular pathologies, is not well-understood. Therefore, technologies for assessment of retinal oxygenation are greatly needed to broaden knowledge, and thereby advance the available diagnostic and therapeutic procedures for retinal diseases. A method for retinal oxygen tension measurement that utilizes oxygen-sensitive microelectrodes is available, but is invasive and does not have the potential to be clinically applicable. Imaging of intravascular oxygen tension based on phosphorescence emission from an oxygen-sensitive molecular probe has been demonstrated, but with limited depth discrimination. We propose to overcome the limitations of the available techniques by combining our technique of optical section retinal imaging with phosphorescence lifetime imaging to provide noninvasive and quantitative measurements of oxygen tension in the retinal vasculatures and tissue. The specific aims are to develop and establish a novel imaging system for generating three-dimensional images of oxygen tension in the chorioretinal vasculatures and retinal tissue, to determine normal baselines for spatial and temporal variations in retinal oxygen tension, to obtain and validate retinal oxygen consumption measurements based on phosphorescence images, and to assess inner retinal oxygen consumption by mapping of retinal oxygen tension gradients and vasculature patterns. The proposed studies will provide a foundation for retinal oxygen tension measurements in normal retinas that is necessary for investigating variations in animal models of retinal diseases in the future. Once refined, the technique will serve as a valuable tool for investigating disease-related oxygen dynamics, and thereby, can significantly impact the understanding of the pathophysiology, diagnosis and treatment of retinal diseases.