Quantifying retinal oxygenation and metabolism by phosphorescence lifetime imaging

The retina is a highly metabolically active tissue, requiring adequate availability of oxygen and other metabolites to generate energy for cellular survival and visual function. Retinal hypoxia has been implicated in several common retinal diseases and associated with the development of vision-threatening pathologies. Since the level of hypoxia determines processes that are activated for either cell survival or death, knowledge of retinal oxygenation is essential. This article reviews depth-resolved quantitative measurements of retinal vascular and tissue oxygen tension in rodents using the technique of phosphorescence lifetime imaging. Furthermore, retinal oxygen metabolic biomarkers were quantitatively derived from oxygen tension measurements and shown to be altered under challenged physiological and pathological conditions. Application of phosphorescence lifetime imaging can be useful for advancing knowledge of retinal ischemia pathophysiology and identifying physiological biomarkers to monitor progression and evaluate therapeutic interventions in animal models of human retinal diseases.