The objective of this project is to explore the feasibility of polarization signal imaging of early receptor potential (ERP) in intact retinas. Previous investigations have demonstrated the existence of polarization signal response due to ERP-associated birefringence change in isolated photoreceptor outer segments activated by visible light. However, imaging of the ERP-associated birefringence change in intact retina is technically challenging because of complex structure of the retina. In principle, both birefringence and scattering changes can produce transient polarization signals in the retina. In order to achieve robust imaging of ERP-associated birefringence change, it is important to reduce the effect of light scattering on the measurement. In this project, we propose to develop a high speed light-field optical coherence tomography (OCT) imager, and to validate it for optical separation of birefringence- and scattering-associated polarization signals. The proposed light-field OCT imager will provide capability of angle-resolved polarization signal imaging. In principle, when an oblique light illumination is used, synthetic angular filters will allow optical separation of light scattering- and birefringence-associated polarization signals in the light activated retina. Isolated lobster nerve axons will be employed as a transition preparation for functional test of the proposed imager. Frog retinal slices and intact retinas will be used to demonstrate the feasibility of polarization signal imaging of ERP-associated birefringence response. Although our ultimate goal is to use the proposed technology to diagnose of retinal diseases, this R21 project will focus on technical development and functional validation of the light-field imaging system. Successful implementation of this project will build a solid foundation for the development of objective, high resolution instruments for photoreceptor function evaluation.
The proposed light-field imager will provide capability of high resolution imaging of stimulus-evoked early receptor potential. High resolution evaluation of photoreceptor response can lead to better study and diagnosis of the retina.
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