An Image Segmentation Method for Glaucoma Detection using the CDR Wanicha Ruengkitpinyo † Toshiaki Kondo † Waree Kongprawechnon † † School of Information, Computer, and Communication Technology (ICT), Sirindhorn International Institute of Technology (SIIT), Thammasat University, Bangkok, THAILAND {ru.wanicha@gmail.com, tkondo@siit.tu.ac.th, waree@siit.tu.ac.th} Abstract Glaucoma is a serious eye disease, overtime it will result in gradual blindness. Early de- tection of the disease will help prevent against developing a more serious condition. Cup-to- Disc ratio or CDR is an important clinical indi- cator for glaucoma diagnosis. Nowadays, CDR is manually determined by trained ophthalmolo- gists and has to be diagnosed by using retinal im- ages from special cameras which are expensive. These are limitations of potential in mass screen- ing for early detection. This paper focused on developing system that can provide suitable way to compute CDR result which give the most ac- curate result and prevent from current limitation. The edge detection with power-law transforma- tion method is described for both optic cup and optic disc segmentation. Keywords: Cup-to-Disc, Optic cup, Optic Disc, Edge Detection, Power Law 1 Introduction Glaucoma is a disease of increased pressure within the eyeball. The increase in pressure re- sult in immoderate amount of stress to be put to the attachment of the optic nerve to the eye [1] [2]. Lack of treatment for glaucoma can lead to permanent blindness, which glaucoma is the sec- ond leading cause worldwide. Early detection of the disease will help prevent against developing a more serious condition. For CDR, diameter of both optic disc and op- tic cup are used. Optic disc is usually known as blind spot. There is no cell to detect light on op- tic disc. Optic disc is bright area which locates at the back of eyeball, while optic cup is the bright- est area within an eyeball. Optic cup diameter for normal case and glaucoma case are shown in Figure 2 [3]. The cup diameter is larger, corre- sponding to the loss of vision. Vertical cup-to- disc ratio value that is greater than or equal to 0.65 is considered to be suspicious for glaucoma [4] [5]. Figure 1. State of human vision. 1.1 Problem Statement Optical Coherence Tomography or OCT is widely used for medical imaging techniques. OCT is an optical signal acquisition and process- ing method which captures optic images in three- dimensional image. Both OCT and ophthalmol- ogists are having the same problem which are insufficient and expensive. They can only find in large hospitals or private hospitals. Some of glaucoma patients are insufficient in funds. This can make patients get a late glaucoma treatment and bad for their eye health. The need of experts and large amount of expenses are limitations of potential in mass screening for early detection. To solve problem of OCT images, fundus im- ages are selected to be input images for this project. Fundus camera is another type of cam- era which can use to capture retina images. Fun- dus camera has less expensive costs compar- Figure 2. Components of eyeball (a) Optic cup and optic disc area within eyeball. (b) Normal optic nerve cell with small optic cup. (c) Glau- comatous optic nerve head.