[Development of image processing system for fundus video-angiography with non-stroboscopic illumination].

A new recording system for fluorescein video-angiography using a highly sensitive color charge coupled device (CCD) camera was developed. An image processing unit installed in a personal computer made it possible to process video signals from the camera and/or a video tape recorder. Functions of the unit are on-line and/or off-line operations on image data such as smoothing, digital subtraction, differentiation etc. Application of the unit improved the quality of images observed on a monitor screen. This system enabled observation of the ocular fundus with illumination of low intensity, which reduced physical and psychological suffering of patients. In addition continuous and whole sequences of fundus fluorographs were recorded, without using strong stroboscopic lights. Extraction of a clear image from ambiguous records at any moment was possible through off-line processing on the stored data. Furthermore quantification of the blood flow in any blood vessels was possible by subtracting two successive images. With this system, quantitative expression of a slight difference in the color of the fundus could be made through calculation of the ratios among R-, G-, and B-components of signals at any place. Finally, comparative study of images of the fundus with natural color could be made with those of fluorography. These features may provide further information on the physiology and pathology of the fundus.