Figure 1: Eye Fundus Image Detection and Localization of Fovea in Human Retinal Fundus Images Khawaja Muhammad Asim 1 , A. Basit 2 , Abdul Jalil 1 1 DCIS. Pakistan Institute of Engineering and Applied Sciences (PIEAS), Nilore, Islamabad 45650, Pakistan 2 TPPD. Pakistan Institute of Nuclear Science and Technology (PINSTECH), Nilore, Islamabad 45650, Pakistan asimkhawaja786@gmail.com, abdulbasit1975@gmail.com, jalil@pieas.edu.pk Abstract— In retinal images, Optic Disc (OD) and fovea are two main structures. To develop an automated system for detection of eye diseases like glaucoma and macular edema, it is necessary to have knowledge of OD and fovea. This paper describes an automated detection of fovea. Detection of fovea is dependent upon approximate location of OD. After obtaining the location of OD, erosion and dilation operations are performed on gray scale fundus images. The region of interest is defined with respect to the location of OD. Since in the case of normal retina image fovea is the darkest spot inside macular region and morphological operations make it more visible than its macula background. So the set of all the darkest spots are detected and their median point is selected as center of fovea. This detected location is then mapped in blood vessel map of retina. If it lies in the vicinity of any blood vessel then image shows signs of macular edema and take the second minimum intensity value for fovea location. Keywords-component; Fovea detection, Fovea loclization, Retinal images, Optic Disc I. INTRODUCTION While examining the normal retinal image, it is found that fovea is a dark portion present on temporal side of Optic Disc (OD) inside macula region as shown in Figure 1. Center of fovea is away from OD about 2-3 times the diameter of OD [1]. Fovea contains cones (light receptors) in its central region, which are responsible for sharp vision. Endeavors are on their way to design automated systems for detection of eye diseases like glaucoma, diabetic retinopathy and macular edema. This research is a small part of such big project. Fovea is harder to detect as compare to OD because it is the smallest part present inside macula region and it has no clear boundary unlike OD. The main properties of fovea that have been used by researchers for its detection are its relative position with respect OD, absence of major blood vessels inside it and its dark color. Several methods [1-5] are available in literature for detection of fovea. This paper presents a precise and fast method for detection of fovea. However it needs the approximate location and diameter of OD as input parameters. We incorporate this by using techniques proposed by Mahfouz et al. [6] and Basit [7]. Proposed method for fovea detection is quite tolerant towards certain abnormalities of retina i.e. lesions and hard exudates. Sinthanayothin et al. [4] in 1999 proposed a method for detection of fovea using a template to find the fovea locus in retinal images. Singh et al. [2] detected fovea using appearance based method. Sekhar et al. [5] used Hough transform and morphological operators to detect fovea in 2008. Most of the methods (available in literature) tend to use the location of OD and blood vessels. Therefore, they do not work properly if the accurate information of OD location and blood vessels is not available. Method proposed in this paper also works accurately if exact location of OD is not known. The only prerequisite is the approximate location of OD and its approximate diameter. If the image possess signs of macular edema at its acute stage, then blood vessels map is also required for accurate detection. During fovea detection entire blood vessels from retinal image are removed using morphological operators. Applying contrast enhancement makes the intensity differences more prominent. Using the approximate coordinates of OD point as a reference, a region of interest (ROI) is defined and then fovea is detected as the darkest portion in the region of interest. If accurate values of OD coordinates or diameter are not known, a wide Optic Disc Fovea 978-1-4673-4451-7/12/$31.00 ©2012 IEEE