A computerized system for localization of diabetic lesions from fundus images

A computerized system for the localization of diabetic lesions from fundus photographs is described. The coordinates for each lesion in relation to reference points are determined from fundus images projected on a digitizing table. The program accepts some variation in coordinates for a single lesion, still to be recorded as the same lesion in a series of photographs, and the magnitude of this variation is adjustable. The data obtained from the localization program are transferred to a register program yielding the following parameters: number of lesions, new lesions, lost lesions, variable lesions, time of presence for lost lesions. These data can be further exported into Microsoft Excel 4, for analysis of large patient materials. An intra-observer error of 0% and an inter-observer error of 1.1% was found in localization of lesions from fundus images. The program was insensitive to small variations in the fundus pictures, but comparisons of 30 degrees and 60 degrees photographs of the same fundus, or 20 degrees deviation of gaze, induced identification errors in 2.9% and 11.9% of localizations, respectively. With this system new parameters on diabetic fundus images can be obtained. The significance of these parameters in the progression of diabetic retinopathy will be analyzed in further studies.