Oxygen Measurements in the Retina Using Phosphorescence Lifetime Imaging

Abstract

Abstract: : Purpose:To obtain accurate maps of the oxygen distribution in the retina of the mouse and piglet and to evaluate their use in detecting vascular lesions and defects in oxygen delivery. Methods:An intensified CCD camera was used to image the phosphorescence from phosphors in the blood through microscope optics. On axis illumination by a modulated LED lamp was used to excite the phosphor and the phosphorescence was imaged at different phase delays relative to excitation. Phosphorescence lifetime and oxygen pressures were calculated for each pixel of the resulting image sets. Results:High resolution maps of the phosphorescence intensity (blood distribution) and oxygen pressure were obtained for the retina of both mice and piglets. Arterioles and veins could be identified by their respective oxygen pressures and oxygen extraction quantitated. Oxygen pressures in the retinal vessels are dependent on systemic blood pressure and arterial oxygenation and these relationships are being investigated. The resolution is shown to be sufficient to identify individual capillaries that are either blocked or for other reasons have low oxygen pressures within the vessel lumen. Conclusions:Phosphorescence lifetime imaging provides high resolution maps of the oxygen distribution in the retina of mice and pigs. These maps are of sufficient resolution that it possible to identify and quantitate any regions of anomalous oxygen delivery/hypoxia that are present, information critical to understanding the role of hypoxia in ocular diseases.

Keywords: hypoxia • retina