Durchmesserbestimmung von Netzhautgefäßabschnitten in digitalen Fundusfotografien - Eine klinische Studie zur Methodik und Reproduzierbarkeit12

Abstract

The aim of this study was the evaluation of new algorithms to measure diameter of segments of retinal branch vessels offline in local dependence and independent by observer. Methods 360 flashed fundus images (camera FF 450 ZEISS Germany, Visualis IMEDOS GmbH Weimar/Germany) of 12 eyes of healthy volunteers (10 independent sessions containing 3 images for every eye) were analysed. Algorithms detect the vessel diameter along the vessel course automatically. Corresponding segments of a retinal artery and vein were examined (mean length of the segment 2.5 mm) in every image of one eye. Results The marked arterial segment was detected automatically in 359 pictures and the venous segment in all pictures. The mean vessel diameter was detected in single pictures with a mean coefficient of variation (CV) for arteries of 3.4 % and for veins of 2.7 %. The differences of arterial and venous diameter between images were not significant. Analyzing sessions the CV of the mean vessel diameter were reduced for arteries to 2.7 % and for veins to 2.5 %. The standard deviation of the mean vessel diameter was independent of the vessel diameter (branch vessels with diameter of 120 to 200 micrometer). The mean CV of the vessel diameter at single locations were 5.7 % for arteries and 3.8 % for veins. Conclusions The new algorithms are useful for retinal vessel analysis, if there are no questions concerning the dynamic of vessel behaviour.

Flicker observation light induces diameter response in retinal arterioles: a clinical methodological study

“…Following correction for the image position, an analysis window was placed over the vessel segment, and the diameter was then measured fully automatically in a procedure similar to that used with the RVA. 22 Again, the mean of the vessel segment was used and, for statistical analysis, the measurements of images of 5 seconds long time slices were combined. Flicker light was generated by means of rectangular interruption of the green observation light of the RVA (530-600 nm, illumination at the fundus approximately 6500 lux) at 12.5 Hz over the entire 30˚image field.…”

“…periodic changes of the observation light simulate luminance flicker to induce diameter changes in retinal arterioles;N the changes are quantifiable by an online automated technique based on the RVA,[19][20][21] as well as by offline analysis of digital images 22. …”

Retinal Blood Flow Evaluation

“…Studies with other techniques have also suggested that autoregulation of retinal and/or ONH BF is reduced in eyes with glaucoma. Thus retinal venous D response to short-term elevations in IOP was found to be altered [9] and changes in rim perfusion after a therapeutic IOP reduction [146] suggest that autoregulation may be defective in eyes with glaucoma while intact in ocular hypertension. Also the increase in ONH BF [147] and D of retinal veins [148] in response to flicker were found to be significantly diminished in glaucoma patients as compared with healthy volunteers, both results being indicative of an impairment of neurally mediated vasoreactivity.…”

“…In recent years, the RVA has markedly simplified this measurement [9,10], allowing also the quasi-continuous recording of D changes evoked by various physiological maneuvers (dynamic measurements) (fig. 1).…”

Statische Gefäßanalyse in nonmydriatischen und mydriatischen Bildern

“…Für retinale Gefäßdurchmesser konnten so in grçßeren epidemiologischen Studien Zusammenhänge zu Inzidenz [10,15] und Prävalenz des arteriellen Hypertonus [5,13], zur Schlaganfallprävalenz [12], Angina pectoris [6] sowie zu weiteren kardiovaskulären Risikofaktoren [3] nachgewiesen werden. Die Mçglichkeiten der digitalen Fundusfotografie und eine weitgehend automatisierte Auswertung [7] ermçglichen heute die Bestimmung von Gefäßdurchmessern in der klinischen Routine. Gerade unter den Alltagsbedingungen der Praxis wie auch von Screeninguntersuchungen [6] [12]: Der Untersucher markiert die Lage der Papille im Bild, nachfolgend wird von der Software der Auswertebereich vorgegeben.…”