Localization of Fovea in Digital Fundus Images

Detection of the position of anatomical structures is essential in an automatic diabetic retinopathy screening system. Using these locations, a frame of reference can be set up in the fundus image. This is essential for two reasons. 1) To successfully find abnormalities in a fundus image, it is essential to mask out the normal anatomical structures from the analysis; and 2) The distribution of the abnormalities associated with diabetic retinopathy is not uniform over the retina. Certain types of abnormalities occur more often in specific areas on the retina. The position of an abnormality relative to the anatomical structures will be useful as a feature for later analysis. This chapter deals with the detection of vascular arcade, macula and fovea. Macula is located at the centre of retina. It is temporal to the optic disk between the main superior and inferior vascular arcades. Fovea is a small depression in the macula and is indicated by a deep-red or red-brown colour in colour fundus images. It is the darkest part in the retinal images. Accurate localization of the foveal region is important to any diagnosis method that is based on the statistical categorization of vision threatening lesions in the retina. In this chapter, a novel approach for detecting vascular arcade, macula and fovea is proposed and also a polar fundal coordinate system is