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Michael Lasta, Agnes Boltz, Doreen Schmidl, Stefan Palkovits, Berthold Pemp, Semira Kaya, Gerhard Garhofer, Leopold Schmetterer; A Study Investigating The Reproducibility Of Retinal Vessel Hemoglobin Oxygenation Saturation Measurements Using The Retinal Vessel Analyzer In Healthy Young Subjects. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5637.
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Measurement of hemoglobin oxygenation saturation in retinal vessels is a difficult task. In the recent years several systems became commercially available. In the present study we used a fundus camera containing a dual wavelength transmission filter and a CCD camera for the assessment of arterial and venous oxygen saturation (Retinal Vessel Analyzer, Imedos, Jena, Germany). Two monochromatic fundus images at a wavelength of 548 and 610 nm are recorded simultaneously, and based on the optical density ratio the oxygen saturation (SaO2) is calculated.
To test the reproducibility of this technique, a study with 14 healthy subjects between 18 and 35 years was performed. Test/retest reproducibility was assessed using data of 3 fundus images. To determine short-term reproducibility a second cycle of 3 fundus images was carried out within approximately 15 minutes. Finally, these cycles of measurements were repeated on another study day to assess day-to-day reproducibility. Data of retinal branch arteries and branch veins were evaluated separately. To calculate reproducibility the standard deviation (SD) of these measurements was used.
In retinal branch arteries a SaO2 of 91±8% (range 77-112%, 40 vessels) was measured, whereas retinal branch veins showed a SaO2 of 49±9% (range 32-69%, 38 vessels). The SD of the test/retest measurements was 3.0±2.3% in retinal branch arteries and 5.4±3.7% in retinal branch veins. The short term SD was 2.9±2.1% in arteries and 4.7±3.7% in veins. Last but not least, a day-to-day SD of 4.0±2.8% in arteries and 6.2±4.1% in veins was measured.
These data indicate that test/retest-, short-term- and day-to-day reproducibility of this technique seems to be acceptable. Hence, the system may be adequate to determine oxygen saturation even in longitudinal studies. Nevertheless, the validity of these measurements requires further studies.
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