In vitro model that approximates retinal damage threshold trends
Without effective in vitro damage models, advances in our understanding of the physics and biology of laser-tissue interaction would be hampered due to cost and ethical limitations placed on the use o...
Laser speckle imaging of atherosclerotic plaques through optical fiber bundles
Laser speckle imaging (LSI), a new technique that measures an index of plaque viscoelasticity, has been investigated recently to characterize atherosclerotic plaques. These prior studies demonstrated ...
Dietrich Schweitzer University of Jena, Department of Ophthalmology, Jena, Germany
Thepurpose of this study was to measure the hemoglobin oxygenationin retinal vessels and to evaluate the sensitivity and reproducibilityof the measurement. Using a fundus camera equipped with aspecial dual wavelength transmission filter and a color charge-coupled devicecamera, two monochromatic fundus images at 548 and 610 nm wererecorded simultaneously. The optical densities of retinal vessels for bothwavelengths and their ratio, which is known to be proportionalto the oxygen saturation, were calculated. From 50-deg images, theused semiautomatic vessel recognition and tracking algorithm recognized and measuredvessels of 100 µm or more in diameter. On average, arterialand venous oxygen saturations were measured at 98±10.1% and 65±11.7%,respectively. For measurements in the same vessel segments from thefive images per subject, standard deviations of 2.52% and 3.25%oxygen saturation were found in arteries and veins, respectively. Respirationof 100% oxygen increased the mean arterial and venous oxygensaturation by 2% and 7% respectively. A simple system fornoninvasive optical oximetry, consisting of a special filter in afundus camera and software, was introduced. It is able tomeasure the oxygen saturation in retinal branch vessels with reproducibilityand sensitivity suitable for clinical investigations.
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