Psychologists of the Gestalt school maintain that objects are recognized as wholes in a parallel procedure: the internal representation is matched with the retinal image in a single operation.

The key process and difficulty to realize compute intelligent auxiliary diagnosis of retinal image is how to automatically ac- quire the pathological information.

Because both vessels and background are locally uniform in retinal images, there must be a threshold which is able to segment vessels precisely in a certain sub-image.