MEASUREMENTS OF THE OXYGEN SATURATION IN RETINAL VESSELS WITH RESPECT TO SPECULAR WALL REFLECTIONS AND VESSEL DIAMETER

97th DOG Annual Meeting 1999

V682
MEASUREMENTS OF THE OXYGEN SATURATION IN RETINAL VESSELS WITH RESPECT TO SPECULAR WALL REFLECTIONS AND VESSEL DIAMETER

E. Thamm, D. Schweitzer, M. Hammer, A. Kolb

The oxygen saturation (OS) in retinal vessels can be measured by Imaging-Ophthalmo-Spectrometry. Significant deviations between venous oxygen saturation of healthy normals and patients indicate an important role of the microcirculation at AMD. A clinical OS analysis was altered by low signal-noise-ratios of the spectra, by reflections at the vessel walls, and by the computation time. Also, there is a diameter dependence which does not fulfil the Lambert-Beer-law in the transmission spectra used as primaries. We demonstrate how in case of symmetric position within the monitored area the vessels specular reflex can be replaced. On the basis of transmis-sion measurements in whole blood with various layer thickness the effect of vessel size is taken into account. An optimized algorithm detects vessels, measueres their size, and calculates the primary data required for the OS analysis. The implementation of digital filters for noise reduction allows the reduction of wavelength data points and, hence, minimizes the computation time to a few seconds.

Friedrich Schiller University Jena, Dept. of Ophthalmology, Bachstr. 18, D - 07740 Jena, Germany

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