{"id":{"repo_id":"auckland-ms","oai_identifier":"oai:researchspace.auckland.ac.nz:2292/47557"},"canonical_url":"https://search.dev.ndltd.org/etd/auckland-ms/oai:researchspace.auckland.ac.nz:2292/47557","repository":{"repo_id":"auckland-ms","name":"University of Auckland","base_url":"https://researchspace.auckland.ac.nz/server/oai/request"},"display":{"title":"Ray Tracing Confirms the Optical Properties of the Bovine Lens Are Actively Maintained by the Microcirculation System","abstract":"Ocular pathologies such as cataract have become increasingly common as the human population continues to age due to better healthcare. As such, the need for an improved understanding of the underlying causes is necessary. Using a variety of Magnetic Resonance Imaging (MRI) modalities and optical modelling software the Molecular Vision Laboratory (MVL) has shown that the lens geometry and the gradient of refractive index (GRIN), which together determine the optical properties of the ocular lens, are actively maintained by the lens microcirculation system. Based on a series of experiments the MVL have proposed that monitoring the optical properties of lens could serve as a good indicator at the whole tissue level of the underlying state of the cellular physiology of the lens. To investigate this hypothesis, I have developed a novel laser ray tracing (LRT) system that allows the optical properties of isolated bovine lenses maintained in organ culture to be measured. A fully automated LRT system capable of passing multiple rays at different projection angles through bovine lenses maintained in organ culture was developed. The lens geometry was quantitatively analysed by detecting the edge of the lens using state of the art segmentation methods. Retrieval of the lens GRIN involved solving an optimization problem that is constructed from information in the ray deflections. This optimization process was aided by a set of physiologically and optically relevant constraints. These constraints included a decreasing refractive index from the lens core radially outward towards the lens surface, and a homogenous index at the surface of the lens, that was consistent with the lens growth rings that are formed during lens development. In some instances, information of the absolute refractive index of the lens was also required. The overall lens optics, determined by the product of the lens geometry and GRIN, was then validated by comparing the ray trajectories computed using ray theory simulations to direct experimental trajectories extracted from the original ray tracing images. I then used this system to monitor the time course of changes to lens geometry, GRIN and power in bovine lenses organ cultured in the absence and presence of reagents known to alter the cellular physiology of the lens. Lenses cultured in Artificial Aqueous Humor (AAH) for up to four hours maintained relatively constant power, geometry and GRIN over time. In contrast, lens incubated in a high concentration of K+ (High K+-AAH), which inhibits the microcirculation system by depolarizing the lens potential, exhibited a rounding in lens geometry, but a decrease in GRIN, which resulted in a small, but significant increase in overall power. A similar effect on lens geometry, GRIN and power was observed in lenses perfused with 100% CO2, which by altering lens pH closes gap junctions in the outer cortex of the lens. In contrast, incubating lenses in ouabain (1 mM), to block the Na+/K+-ATPase that drives the lens microcirculation, caused a more pronounced rounding of lens shape, an increase in GRIN that was more prominent in the lens core relative to the outer cortex, and a substantial increase in optical power. Using LRT to directly measure lens optics I have confirmed earlier MRI experiments that showed the microcirculation system actively controls the optical properties of the lens. Furthermore, I have shown that inhibiting different components (lens potential, gap junctional conductance and Na+ pump current) of the lens microcirculation system differentially affects the lens optical properties.","abstract_html":"Ocular pathologies such as cataract have become increasingly common as the human population continues to age due to better healthcare. As such, the need for an improved understanding of the underlying causes is necessary. Using a variety of Magnetic Resonance Imaging (MRI) modalities and optical modelling software the Molecular Vision Laboratory (MVL) has shown that the lens geometry and the gradient of refractive index (GRIN), which together determine the optical properties of the ocular lens, are actively maintained by the lens microcirculation system. Based on a series of experiments the MVL have proposed that monitoring the optical properties of lens could serve as a good indicator at the whole tissue level of the underlying state of the cellular physiology of the lens. To investigate this hypothesis, I have developed a novel laser ray tracing (LRT) system that allows the optical properties of isolated bovine lenses maintained in organ culture to be measured. A fully automated LRT system capable of passing multiple rays at different projection angles through bovine lenses maintained in organ culture was developed. The lens geometry was quantitatively analysed by detecting the edge of the lens using state of the art segmentation methods. Retrieval of the lens GRIN involved solving an optimization problem that is constructed from information in the ray deflections. This optimization process was aided by a set of physiologically and optically relevant constraints. These constraints included a decreasing refractive index from the lens core radially outward towards the lens surface, and a homogenous index at the surface of the lens, that was consistent with the lens growth rings that are formed during lens development. In some instances, information of the absolute refractive index of the lens was also required. The overall lens optics, determined by the product of the lens geometry and GRIN, was then validated by comparing the ray trajectories computed using ray theory simulations to direct experimental trajectories extracted from the original ray tracing images. I then used this system to monitor the time course of changes to lens geometry, GRIN and power in bovine lenses organ cultured in the absence and presence of reagents known to alter the cellular physiology of the lens. Lenses cultured in Artificial Aqueous Humor (AAH) for up to four hours maintained relatively constant power, geometry and GRIN over time. In contrast, lens incubated in a high concentration of K+ (High K+-AAH), which inhibits the microcirculation system by depolarizing the lens potential, exhibited a rounding in lens geometry, but a decrease in GRIN, which resulted in a small, but significant increase in overall power. A similar effect on lens geometry, GRIN and power was observed in lenses perfused with 100% CO2, which by altering lens pH closes gap junctions in the outer cortex of the lens. In contrast, incubating lenses in ouabain (1 mM), to block the Na+/K+-ATPase that drives the lens microcirculation, caused a more pronounced rounding of lens shape, an increase in GRIN that was more prominent in the lens core relative to the outer cortex, and a substantial increase in optical power. Using LRT to directly measure lens optics I have confirmed earlier MRI experiments that showed the microcirculation system actively controls the optical properties of the lens. Furthermore, I have shown that inhibiting different components (lens potential, gap junctional conductance and Na+ pump current) of the lens microcirculation system differentially affects the lens optical properties.","abstract_has_math":false,"creators":["Qiu, Chen"],"institution":"ResearchSpace@Auckland","degree_name":"PhD","degree_level":"Doctoral","degree_discipline":"Biomedical Engineering","degree_department":null,"school":null,"contributors":[],"advisors":["Donaldson, P","Vaghefi, E","Turuwhenua, J"],"committee_chairs":[],"committee_members":[],"year":2019,"date_issued":"2019","date_published":"2019","updated_at":"2026-07-24T01:05:49Z","subjects":[],"languages":[],"rights":["Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. 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Using a variety of Magnetic Resonance Imaging (MRI) modalities and optical modelling software the Molecular Vision Laboratory (MVL) has shown that the lens geometry and the gradient of refractive index (GRIN), which together determine the optical properties of the ocular lens, are actively maintained by the lens microcirculation system. Based on a series of experiments the MVL have proposed that monitoring the optical properties of lens could serve as a good indicator at the whole tissue level of the underlying state of the cellular physiology of the lens. To investigate this hypothesis, I have developed a novel laser ray tracing (LRT) system that allows the optical properties of isolated bovine lenses maintained in organ culture to be measured. A fully automated LRT system capable of passing multiple rays at different projection angles through bovine lenses maintained in organ culture was developed. The lens geometry was quantitatively analysed by detecting the edge of the lens using state of the art segmentation methods. Retrieval of the lens GRIN involved solving an optimization problem that is constructed from information in the ray deflections. This optimization process was aided by a set of physiologically and optically relevant constraints. These constraints included a decreasing refractive index from the lens core radially outward towards the lens surface, and a homogenous index at the surface of the lens, that was consistent with the lens growth rings that are formed during lens development. In some instances, information of the absolute refractive index of the lens was also required. The overall lens optics, determined by the product of the lens geometry and GRIN, was then validated by comparing the ray trajectories computed using ray theory simulations to direct experimental trajectories extracted from the original ray tracing images. I then used this system to monitor the time course of changes to lens geometry, GRIN and power in bovine lenses organ cultured in the absence and presence of reagents known to alter the cellular physiology of the lens. Lenses cultured in Artificial Aqueous Humor (AAH) for up to four hours maintained relatively constant power, geometry and GRIN over time. In contrast, lens incubated in a high concentration of K+ (High K+-AAH), which inhibits the microcirculation system by depolarizing the lens potential, exhibited a rounding in lens geometry, but a decrease in GRIN, which resulted in a small, but significant increase in overall power. A similar effect on lens geometry, GRIN and power was observed in lenses perfused with 100% CO2, which by altering lens pH closes gap junctions in the outer cortex of the lens. In contrast, incubating lenses in ouabain (1 mM), to block the Na+/K+-ATPase that drives the lens microcirculation, caused a more pronounced rounding of lens shape, an increase in GRIN that was more prominent in the lens core relative to the outer cortex, and a substantial increase in optical power. Using LRT to directly measure lens optics I have confirmed earlier MRI experiments that showed the microcirculation system actively controls the optical properties of the lens. Furthermore, I have shown that inhibiting different components (lens potential, gap junctional conductance and Na+ pump current) of the lens microcirculation system differentially affects the lens optical properties."]},{"key":"dc:title","label":"Title","values":["Ray Tracing Confirms the Optical Properties of the Bovine Lens Are Actively Maintained by the Microcirculation System"]}]}],"canonical_facts":{"dc:contributor.advisor":["Donaldson, P","Vaghefi, E","Turuwhenua, J"],"dc:creator":["Qiu, Chen"],"dc:date.accessioned":["2019-08-26T23:35:02Z"],"dc:date.issued":["2019"],"dc:description.abstract":["Ocular pathologies such as cataract have become increasingly common as the human population continues to age due to better healthcare. As such, the need for an improved understanding of the underlying causes is necessary. Using a variety of Magnetic Resonance Imaging (MRI) modalities and optical modelling software the Molecular Vision Laboratory (MVL) has shown that the lens geometry and the gradient of refractive index (GRIN), which together determine the optical properties of the ocular lens, are actively maintained by the lens microcirculation system. Based on a series of experiments the MVL have proposed that monitoring the optical properties of lens could serve as a good indicator at the whole tissue level of the underlying state of the cellular physiology of the lens. To investigate this hypothesis, I have developed a novel laser ray tracing (LRT) system that allows the optical properties of isolated bovine lenses maintained in organ culture to be measured. A fully automated LRT system capable of passing multiple rays at different projection angles through bovine lenses maintained in organ culture was developed. The lens geometry was quantitatively analysed by detecting the edge of the lens using state of the art segmentation methods. Retrieval of the lens GRIN involved solving an optimization problem that is constructed from information in the ray deflections. This optimization process was aided by a set of physiologically and optically relevant constraints. These constraints included a decreasing refractive index from the lens core radially outward towards the lens surface, and a homogenous index at the surface of the lens, that was consistent with the lens growth rings that are formed during lens development. In some instances, information of the absolute refractive index of the lens was also required. The overall lens optics, determined by the product of the lens geometry and GRIN, was then validated by comparing the ray trajectories computed using ray theory simulations to direct experimental trajectories extracted from the original ray tracing images. I then used this system to monitor the time course of changes to lens geometry, GRIN and power in bovine lenses organ cultured in the absence and presence of reagents known to alter the cellular physiology of the lens. Lenses cultured in Artificial Aqueous Humor (AAH) for up to four hours maintained relatively constant power, geometry and GRIN over time. In contrast, lens incubated in a high concentration of K+ (High K+-AAH), which inhibits the microcirculation system by depolarizing the lens potential, exhibited a rounding in lens geometry, but a decrease in GRIN, which resulted in a small, but significant increase in overall power. A similar effect on lens geometry, GRIN and power was observed in lenses perfused with 100% CO2, which by altering lens pH closes gap junctions in the outer cortex of the lens. In contrast, incubating lenses in ouabain (1 mM), to block the Na+/K+-ATPase that drives the lens microcirculation, caused a more pronounced rounding of lens shape, an increase in GRIN that was more prominent in the lens core relative to the outer cortex, and a substantial increase in optical power. Using LRT to directly measure lens optics I have confirmed earlier MRI experiments that showed the microcirculation system actively controls the optical properties of the lens. Furthermore, I have shown that inhibiting different components (lens potential, gap junctional conductance and Na+ pump current) of the lens microcirculation system differentially affects the lens optical properties."],"dc:identifier.uri":["https://hdl.handle.net/2292/47557"],"dc:publisher":["ResearchSpace@Auckland"],"dc:relation.isreferencedby":["UoA99265190813502091"],"dc:rights":["Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. 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