Feasibility of noninvasive imaging of chorioretinal oxygenation

The feasibility of an optical system for noninvasive imaging of chorioretinal oxygenation was evaluated. Due to its depth discrimination, this optical section imaging technique has potential for differential imaging of oxygen tension in the chorioretinal vasculatures.

The method consisted of projecting a narrow laser line obliquely on the retina after intravenous injection of an oxygen-sensitive probe and imaging the phosphorescence emission. Due to the angle between the incident laser and imaging path, a phosphorescence optical section image of the retina was captured. The phosphorescence intensity was measured in the chorioretinal vasculatures. The method was tested in three rats while breathing 10% oxygen, 50% oxygen, and room air.

On the phosphorescence optical section image, vasculatures appeared laterally displaced according to their depth location, displaying probe phosphorescence separately in the chorioretinal vasculatures. Oxygenation increased in all vasculatures with increased inhaled percent oxygen. Oxygenation in the retinal artery was 2.3, 1.9, and 1.6 times oxygenation in the retinal vein, capillary, and choroid, respectively. During hypoxia, oxygenation decreased by 28%, 18%, 22%, and 14% in the retinal vein, artery, capillary, and choroid, respectively. During hyperoxia, oxygenation increased by 30%, 45%, 36%, and 28% in the retinal vein, artery, capillary, and choroid, respectively.

The results demonstrate the feasibility of this technique for noninvasive and separate imaging of chorioretinal oxygenation and its potential for three-dimensional oxygen tension imaging.