[Determination of the circulation in the human retina using image analysis of video-angiograms]

Abstract

A method is described to determine the total retinal blood flow. Intravenous fluorescence angiography is the clinical procedure used, together with digital image processing methods. Our system consists of a standard fundus camera, a highly sensitive sensor with a low-light-level intensifier (micro-channal plate) and a CCD, a computer system including a real-time memory, an image display subsystem, and other standard peripherals (disk, magtape, terminal, etc.). The recording speed is 100 frames (noninterlaced), the image size 256 X 256 pixels, and the depth 8 bit. In order to properly track the images against the patients eye movements, it is necessary to have absolutely sharp pictures. The fundus camera is therefore equipped with a stroboscopic bulb, which gives light pulses of 0.01 ms. The stroboscope is synchronized by the electronics of the camera. After recording the images, further evaluation is done.