Fig. 1.

The Gabor filter algorithm for the automatic extraction of retinal surface vessels based on the approach of Oloumi et al.²⁵ The RGB image is converted into grayscale, then an averaged background is subtracted to reduce the effects on any nonuniformities in illumination. The contrast between the FOV and the background is then reduced before oriented Gabor filters of up to three scales are applied to the filtered image. The outputs of the Gabor filtering stage are combined, a threshold applied before the images are postprocessed and the image pixels labeled as vessel or background (see text for details).