Quantitative characterization of vitreous degeneration in myopia

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DESCRIPTION (provided by applicant): The ultimate goal of this project is to develop a quantitative, ultrasound-based assessment of the vitreous as it relates to vitreo-retinal diseases, such as myopia and diabetic retinopathy, at an early stage before severe outcomes (e.g., blindness) occur. Normal age-related changes (e.g., collagen cross-linking and aggregation, liquefaction, cellular debris, etc.) create inhomogeneities, such as floaters, to appear throughout the vitreous in a non-uniform distribution; these inhomogeneities can serve as weak acoustic scatterers. Concurrent changes at the vitreo-retinal interface weaken the adhesion of the posterior vitreous cortex to the internal limiting lamina of the retina, resulting in posterior viteous detachment. For patients with myopia, these normal processes do not typically occur in tandem because liquefaction is accelerated and the vitreous destabilizes before the vitreous adhesion to the retina is weakened. No diagnostic method is now available to characterize the changes taking place throughout the vitreous volume at an early stage before irreversible pathologies have developed or to determine how these changes relate to progression of diseases. Thus, a clinical need exists to detect within the vitreous the macromolecular changes and structural precursors related to vitreo-retinal disease. We will assemble a novel, high-resolution, annular-array ultrasound system capable of acquiring image data of the entire vitreous and then use quantitative ultrasound methods to characterize vitreous inhomogeneities based on parameters derived from raw ultrasound backscatter signals. The system will utilize state-of-the-art, 20-MHz, annular-array technology to achieve an unprecedented improvement in depth-of-field, resolution and sensitivity relative to current clinical ultrasound technology. The proposed technology will overcome limitations of optical coherence tomography, such as its restricted lateral view through the pupil (due to opaque intervening structures such as the iris, sclera, and possibly cataracts) and its inability to image optically transparent tissue. The early stages of th project will emphasize assembling a hand-held clinical prototype annular-array system and developing signal-processing methods. Later stages will focus on human-subject imaging and quantification of vitreous inhomogeneities occurring during normal aging and myopia.