Screening of Diabetic Retinopathy - Automatic Segmentation of Optic Disc in Colour Fundus Images

In this paper, a novel approach to automatically segment the optic disc contour using the center point of an optic disc candidate is proposed. The optic disc segmentation algorithm consists of 2 stages. The first stage involves the removal of blood vessels that obscure the optic disc. The blood vessel structures are detected using morphological operations. These detected structures are then removed by anisotropic diffusion smoothing. The second stage involves the detection of edge points belonging to the optic disc-contour. A number of one dimensional intensity profiles which pass through the center point of optic disc region are then obtained at multiple angles with fixed angular intervals. The modulus maxima of each intensity profile are identified as a contour point for the optic disc. Among these contour points, some of the outliers are removed by re-positioning to a new position which complies with optic disc´s shape using spline interpolation. Using these contour points, a coarse contour of the optic disc is constructed. Testing the approach on 23 colour fundus images demonstrates that the proposed algorithm is able to detect the optic disc contour to an accuracy of 92% to that drawn by a human expert