A novel method for volumetric oxygen mapping in living retina

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PROJECT SUMMARY It is widely accepted that oxygen deficiency is a culprit and a marker of several major retinal diseases, including diabetic retinopathy, age-related macular degeneration, glaucoma etc. However, it remains to be extremely challenging to measure oxygen in vivo in the eye, and no tools currently exist that can provide 3D oxygen distributions in the retina with high spatial resolution at appropriate imaging speeds. The goal of this project is to overcome these limitations and develop a new optical imaging technique for volumetric oxygen mapping in retina. Our approach will leverage the recently developed potent oxygen probes (such as Oxyphor 2P), whose phosphorescence decay times serve as quantitative markers of local oxygen partial pressures (pO2) in living tissues. To enable volumetric imaging with high throughput, we propose to develop a novel imaging instrument, termed oblique scanning laser ophthalmoscope (oSLO). oSLO is based on the concept of single lens scanned light sheet microscopy and enables volumetric phosphorescence lifetime imaging without time- consuming plane-by-plane pixel-wise sectioning. Our new method should be able to achieve 10 kilohertz voxel rate that is three orders of magnitude higher than the current state-of-the-art two-photon phosphorescence lifetime microscopy (2PLM). In this project we will: (Aim 1) develop a phosphorescence lifetime-based oSLO for volumetric pO2 mapping in living retina in mouse. The new design will allow parallel detection of signals at depth from each scanned location, so that the need in conventional depth sectioning is eliminated and imaging throughput is greatly increased. We will (Aim 2) dynamically image responses of retina and choroid to systemic hypoxia challenge using Oxyphor 2P. We will (Aim 3) then bridge oSLO measurements and label-free applications by multimodal imaging with visible light optical coherence tomography (vis-OCT). Using vascular pO2 as the ground-truth, we will develop a deep spectral training (DSL) algorithm to supervise the inverse calculation of vis-OCT for robust and reliable label-free retinal oximetry. This study will enable the first direct quantitative imaging of interactions between the two circulatory systems in retina (i.e. retinal and choroidal circulation), providing unprecedented information about retinal oxygen supply. IMPACT ON PUBLIC HEALTH: Successful completion of this program will deliver a new ground-breaking methodology for mapping oxygen in the retina that will greatly improve our understanding of retinal diseases.