June 2013
Volume 54, Issue 15
Free
ARVO Annual Meeting Abstract  |   June 2013
Standardization of Retinal Vessel Oximetry and the Influence of Vessel Diameter
Author Affiliations & Notes
  • Sveinn Hardarson
    Faculty of Medicine, University of Iceland, Reykjavik, Iceland
    Department of Ophthalmology, Landspítali University Hospital, Reykjavik, Iceland
  • Sindri Traustason
    Department of Ophthalmology, Glostrup Hospital, Glostrup, Denmark
    Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
  • Jona Kristjansdottir
    Faculty of Medicine, University of Iceland, Reykjavik, Iceland
    Department of Ophthalmology, Landspítali University Hospital, Reykjavik, Iceland
  • Olof Olafsdottir
    Faculty of Medicine, University of Iceland, Reykjavik, Iceland
  • Thorunn Eliasdottir
    Department of Ophthalmology, Landspítali University Hospital, Reykjavik, Iceland
  • Thor Eysteinsson
    Faculty of Medicine, University of Iceland, Reykjavik, Iceland
    Department of Ophthalmology, Landspítali University Hospital, Reykjavik, Iceland
  • Einar Stefánsson
    Faculty of Medicine, University of Iceland, Reykjavik, Iceland
    Department of Ophthalmology, Landspítali University Hospital, Reykjavik, Iceland
  • Footnotes
    Commercial Relationships Sveinn Hardarson, Oxymap ehf. (F), Oxymap ehf. (I), Oxymap ehf. (C), Oxymap ehf. (R), Patent no. 7774036 (P), Patent application 13/377,749 (P), Optos plc. (F); Sindri Traustason, Novartis (F), Oxymap (R); Jona Kristjansdottir, Optos plc. (F); Olof Olafsdottir, None; Thorunn Eliasdottir, None; Thor Eysteinsson, Oxymap ehf (I), Oxymap ehf (S); Einar Stefánsson, Oxymap ehf (P), Oxymap ehf (I), Oculis ehf (P), Oculis ehf (I), Risk ehf (I), Acta Ophthalmologica (E)
  • Footnotes
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Investigative Ophthalmology & Visual Science June 2013, Vol.54, 48. doi:
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      Sveinn Hardarson, Sindri Traustason, Jona Kristjansdottir, Olof Olafsdottir, Thorunn Eliasdottir, Thor Eysteinsson, Einar Stefánsson; Standardization of Retinal Vessel Oximetry and the Influence of Vessel Diameter. Invest. Ophthalmol. Vis. Sci. 2013;54(15):48.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract
 
Purpose
 

The purpose of the study was to develop and test a standardized method for determining the mean retinal vessel oxygen saturation within an eye.

 
Methods
 

The retinal oximeter (Oxymap, Reykjavik, Iceland) simultaneously captures fundus images at 570nm and 600nm. Custom made software analyzes the images and estimates retinal vessel oxygen saturation. Twenty healthy individuals (age 20 to 30 years) were measured according to the analysis standard shown in the figure. Blood flow in the large vessels is related to the fourth power of the diameter and an adjustment was made accordingly to calculate the weighted mean saturation for the whole retina. Additionally, ten images of one individual were measured to estimate the stability of the measurements.

 
Results
 

The table shows the average saturation values, with and without weighing with diameter in the power of four (n=20, mean±SD). The standard deviation for repeated measurements of arterioles in the same eye was 0.30 percentage points for simple means and 0.31 percentage points for means weighted with diameter in the power of four. The corresponding numbers for venules were 1.29 percentage points (simple means) and 1.94 percentage points (weighted means). Retinal venous oxygen saturation decreased by 2.0 percentage points per pixel (≈9μm) of increased diameter (mixed model linear regression, p<0.0001). No significant relationship was detected between arteriolar saturation and diameter (-0.3 percentage points per pixel, p=0.11)

 
Conclusions
 

Weighing the average saturation with the fourth power of vessel diameter, which is a surrogate for weighing with blood flow, yields considerably lower venous saturation, compared to a simple mean. Repeatability of the measurements is good, both with and without weighing the mean. Retinal venous oxygen saturation decreases with vessel diameter, even after correction for artificial effects.

 
 
Figure. Analysis protocol. All vessels above minimum diameter and minimum length are measured close to the optic disc.
 
Figure. Analysis protocol. All vessels above minimum diameter and minimum length are measured close to the optic disc.
   
Keywords: 688 retina • 635 oxygen • 550 imaging/image analysis: clinical  
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