Choroidal and retinal oximetry

• Main Author: Jóna Valgerður Kristjánsdóttir 1985-
• Other Authors: Háskóli Íslands
• Format: Thesis
• Language: English
• Published: 2014
• Subjects: Líf- og læknavísindi; Sjónhimna; Augnsjúkdómar; Iceland
• Online Access: http://hdl.handle.net/1946/17137

Purpose The retinal blood vessels are easily accessible for imaging with specialised fundus cameras. Relative haemoglobin oxygen saturation of retinal vessels can be calculated with a spectrophotometric technique based on decades of research. Recently, a group of researchers in Iceland have developed a non-invasive fundus-camera- based retinal oximeter and specialised software to acquire fundus images and calculate oxygen saturation in retinal vessels. The oximeter has been validated and is sensitive to changes in oxygen saturation and vessel diameter and gives repeatable and reliable results. The oximeter has also given valuable results on oxygen metabolism in various eye diseases. These measurements are limited to retinal blood vessels and cannot measure the vessels of the choroid which supply oxygen to the outer retina, including the highly metabolically active photoreceptors. Another limitation of the fundus-camera-based oximetry is that images view up to 50° of the retina while other retinal cameras such as a scanning laser ophthalmoscope can view up to 200° of the retina. The overall aim of this project was to develop techniques which could address these limitations. More specifically, the first aim was, to test the possibility of measuring the oxygen saturation of choroidal vessels with a fundus-camera-based retinal oximeter and secondly, to test if the oxygen saturation of the retinal vessels can be measured with a scanning laser ophthalmoscope (SLO). Methods Two kinds of oximeters were used to measure oxygen saturation of retinal and choroidal blood vessels. One is based on a conventional fundus camera (Oxymap T1) which uses filtered white light for image acquisition. The other is a scanning laser ophthalmoscope (Optomap 200Tx) which uses lasers for image acquisition. Oxymap Analyzer software processes the images from both cameras and calculates relative haemoglobin oxygen saturation for vessels. Both fundus cameras use two wavelengths to image the fundus. The ratio between light absorbance of blood ...