Abstract
Ophthalmoscopic findings have been considered as an important factor in multiphasic screening systems, or in the diagnosis of the hypertensive disease. However, the study of its automatic and quantitative analyzing system has never been tried.
In this paper, the authors have made an trial to classify the grade of changes at the arterio-venous crossing in the retina, with development of such an analyzing system in fundus photography as a final goal.
Important technical points for developing such a system are as follows :
1 Analysis of chromatic characteristics in the fundus photographs, and a translation technique of photo-images to electrical-images, which should be improved in signal to noise ratio using above result (pre-processing).
2 Extraction technique of contour lines of blood vessels from above images (feature extraction).
3 Quantitative classification of the grade of the diseases by the analysis of above contour lines (recognition).
This report is concerned with the second and third points.
Results obtained were as follows :
1 The minimum value of the diameter of the retinal vein normalized by, its mean value was found to be a good measure in classifying the crossing phenomena.
2 The two-stage extraction method, i. e., the coarse extraction and the precise extraction, was found to be useful for extracting contour lines of blood vessels, which included some new techniques for the image processing.
Using above results, the normal patterns and abnormal patterns in the crossing phenomena were successfully distinguished at the accuracy of 90 percent.
