Retinal oximetry

• Main Author: Sveinn Hákon Harðarson 1978-
• Other Authors: Háskóli Íslands
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2012
• Subjects: Doktorsritgerðir; Augnsjúkdómar; Gláka; Sjónhimna; Iceland
• Online Access: http://hdl.handle.net/1946/12721

Purpose Malfunction of retinal blood flow or oxygenation is believed to be involved in various diseases. Among them are retinal vessel occlusions, diabetic retinopathy and glaucoma. Reliable, non-invasive technology for retinal oxygen measurements has been scarce and most of the knowledge on retinal oxygenation comes from animal studies. This thesis describes human retinal oximetry, performed with novel retinal oximetry technology. The thesis describes studies on retinal vessel oxygen saturation in (1) light and dark in healthy volunteers, (2) central retinal vein occlusion, (3) branch retinal vein occlusion, (4) central retinal artery occlusion, (5) diabetic retinopathy, (6) patients undergoing glaucoma surgery and (7) patients taking glaucoma medication. Methods The retinal oximeter (Oxymap ehf., Reykjavik, Iceland) is based on a fundus camera. An attached image splitter allows the simultaneous capture of four images of the same area of the fundus. Two images are used for further analysis, one acquired with 586 nm light and one with 605 nm light. Light absorbance of retinal vessels is sensitive to oxygen saturation at 605 nm but not at 586 nm. Measurement of reflected light at these wavelengths allows estimation of oxygen saturation in the main retinal vessels. This is performed with custom-made analysis software. Results Light and dark: After 30 minutes in the dark, oxygen saturation in retinal arterioles of healthy volunteers was 92±4% (mean±SD, n=15). After 5 minutes in 80 cd/m2 light, the arteriolar saturation was 89±5%. The decrease was statistically significant (p=0.008). The corresponding values for retinal venules were 60±5% in the dark and 55±10% in the light (p=0.020). Similar results were found after alternating 5 minute periods of darkness and light. In a second experiment (n=19), a significant decrease in retinal vessel oxygen saturation was found in 100 cd/m2 light compared to darkness but 1 and 10 cd/m2 light had no significant effect. Central retinal vein occlusion: In patients with central ...