Fluorescence Lifetime Imaging Ophthalmoscopy PDF Download

"The retina is the light-sensitive tissue at the back of the eye which carries out the first steps in vision. Specialized neural cells in the retina known as photoreceptors are responsible for detection of light and its transduction by initiating an electrical signal to the brain. Adaptive optics scanning light ophthalmoscopy (AOSLO), which dynamically corrects aberrations of the ocular media in the living eye and affords a lateral resolution of 2 ?m, has revolutionized our ability to visualize photoreceptors and many other microstructures in the retina. The implementation of two-photon excited fluorescence (TPEF) imaging in AOSLO has enabled not only complementary structural information throughout the retina, but an objective, non-invasive measure of visual function in photoreceptors by measuring TPEF kinetics from these cells. The aim of the present thesis is to further develop and apply TPEF ophthalmoscopy as a novel measure of in vivo cellular function in the retina. First, TPEF ophthalmoscopy was used in conjunction with other imaging modalities to evaluate the extent of photoreceptor dysfunction in a non-human primate model of retinal degeneration. TPEF ophthalmoscopy was essential in determining that photoreceptors were non-functional. Second, the sensitivity of TPEF kinetics to detect changes in photoreceptor function in conditions relevant to disease pathogenesis was investigated. Systemic hypoxia was employed in non-human primates as a model of physiological change, reducing oxygen supply to the retina, and TPEF kinetics were shown to be slowed as a consequence. Finally, the capabilities of TPEF ophthalmoscopy were expanded by implementing intrinsic fluorescence lifetime imaging. TPEF lifetime imaging was shown to distinguish retinal cell classes that are functionally disparate, and lifetimes were altered in regions of retinal damage. TPEF ophthalmoscopy has the potential to yield advances in understanding of both the basic physiology and pathology of the retina. If translated successfully into humans, TPEF ophthalmoscopy demonstrates promise as a valuable imaging modality that may, when used in conjunction with other clinical measures, identify early cellular dysfunction and longitudinally track pathological changes. Ultimately, it may assist in timely diagnosis, intervention, and development of treatments or vision restoration methods to combat blindness as a consequence of retinal disease."--Pages xiv-xv.