There is perhaps more to examining digital images obtained by computer screening than simple observation by 'untrained' operators. It would appear that software algorithms are available which will detect potential problems from a single image. Once more than one digital image is available for examination software can also be used to highlight changes between two or more images of the same eye taken at different time points.
I surmise that the screening process has more to do with eliminating those without problems that might require intervention thus releasing the highly trained resources to concentrate on individuals where potential problems have been identified. Have a rake on the web:-
2.1 Automatic methods
As mentioned previously, the diagnosis of diabetic retinopathy can be divided into the
following two categories:
1. Screening of the diabetic retinopathy
2. Monitoring of the diabetic retinopathy
Most automatic systems approach the detection directly using shape, color, and domain
knowledge of diabetic retinopathy findings, but the abnormalities can also be found indirectly
by detecting changes between two fundus images taken from the same eye
in different time moment [8, 14]. The direct approach contributes to screening of the
disease, where indirect approach contributes to both screening and monitoring of the
diabetic retinopathy. Both approaches use roughly the following stages for finding abnormalities
in fundus images: 1) image enhancement 2) candidate diabetic retinopathy
finding detection 3) classification to correct diabetic retinopathy category (or hypothesis
rejection).
Some of the main features distinguishing between the different findings and normal
fundus parts are the color and brightness. The same features have been verified also by
ophthalmologists