Abstract
Abstract: :
Purpose: To obtain accurate maps of the oxygen distribution in the retina and choroid of the mouse and determine the efficacy of these measurements for identifying small vascular lesions. Methods: An intensified CCD camera was used to image phosphorescence from a phosphor dissolved in the blood through microscope optics. On axis illumination by a modulated LED light source was used to excite the phosphor and the phosphorescence was imaged at different phase delays relative to excitation. The phosphorescence lifetime was calculated and oxygen pressure is calculated for each pixel from the oxygen dependence of the phosphorescence lifetime. Results: High resolution images were obtained of the phosphorescence from the retina of the mouse eye at measured with each of several different phase delays of 0 to 360 degrees relative to the excitation light. This image set allowed accurate calculation of phosphorescence lifetime and oxygen pressure at each pixel of the image set. Arterioles and veins could be identified by their respective oxygen pressures. Vascular lesions induced by a laser focused to 75 micron spot diameter were readily observed 2 days later by the local region of hypoxia at each lesion site. Individual small vessels have been observed to have abnormally low oxygen levels in 2 yr old mice. Further development will be necessary to fully resolve the oxygen maps of the retina and choroid but this appears technically feasible. Conclusions: Phosphorescence lifetime imaging can provide high resolution maps of the oxygen distribution in the retina of the mouse eye. These maps make it possible to identify and quantitate any regions of hypoxia present in the retina and choroid, information critical to understanding the role of hypoxia in diseases of the eye.
Keywords: hypoxia • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • vascular occlusion/vascular occlusive disease