Retinal Tissue Oxygen Tension Imaging in the Rat

PURPOSE. To report an imaging technique for measurement of oxygen tension (PO(2)) in retinal tissue and establish its feasibility for measuring retinal PO(2) variations in rat eyes by adjusting the fraction of inspired oxygen (FiO(2)). METHODS. A narrow laser line was projected at an angle on the retina, and phosphorescence emission was imaged after intra-vitreal injection of an oxygen-sensitive molecular probe. A frequency-domain approach was used for phosphorescence lifetime measurements. Retinal PO(2) maps were computed from phosphorescence lifetime images, and oxygen profiles through the retinal depth were derived in rats in conditions of 10%, 21%, and 50% FiO(2). RESULTS. Retinal PO(2) measurements were repeatable, and variations in outer and inner retina PO(2) at different locations along the image were not significant (P >= 0.3). Maximum outer retinal PO(2) obtained in 10%, 21%, and 50% FiO(2) were significantly different (P < 0.0001). Maximum outer retinal PO(2) correlated with systemic arterial PO(2) (R = 0.70; P < 0.0001). The slope of the outer retina PO(2) profile correlated with maximum outer retinal PO(2) (R = 0.84; P < 0.0001). Mean inner retina PO(2) correlated with maximum outer retinal PO(2) (R = 0.88; P < 0.0001). CONCLUSIONS. A technique has been developed for quantitative mapping of retinal tissue oxygen tension with the potential to enable sequential monitoring of retinal oxygenation in health and disease. (Invest Ophthalmol Vis Sci. 2010;51:4766 - 4770) DOI:10.1167/iovs.09-4710