Optic disc (OD) is an important part of the eye. In developing systems automatic OD detection is an important step for automated diagnosis of various serious ophthalmic diseases such as Diabetic retinopathy, Glaucoma, hypertension, etc. The variation of intensity within the optic disc and intensities close to the optic disc boundary are the major hurdle in automated optic disc detection. General edge detection algorithms are frequently unsuccessful to segments the optic disc because of this. Complexity increases due the presence of blood vessels. This paper presents a simple method for OD segmentation by using techniques such as Principal Component Analysis (PCA), Mathematical Morphology and Circular Hough Transform. PCA used for good presentation of the input image and mathematical morphology is used to remove blood vessels from image. Circular Hough Transform is used for boundary segmentation.
Keywords—Diabetic retinopathy; glaucoma; optic disc; principal component analysis.
he OD is an important part of the human eye. Human eye receives a light and is carried through the optic nerve to the brain. The optic disc is the point from where the optic nerve exits the eye, the anatomy of the human eye is shown in the Fig.1. To respond a light there is no presence of the light sensitive rods at this point so, there is a break in the field of vision. The entry point of the blood vessels that supplies the retina is at the OD. The optic nerve head in a normal human eye carries millions of neurons from the eye towards the brain. The position of the OD is 3 to 4mm to the nasal side of the fovea. It is a slightly oval shape, with average dimensions of 1.82mm horizontally by 1.92mm vertically.
The OD is considered as one of the main feature which usually appears as a round region brighter than surrounding in fundus image Fig.2.
Visual impairment is a major health problem. The change in the shape or size of OD is an indicator of various ophthalmic pathologies. Diabetic retinopathy, hypertension, glaucoma, and macular degeneration are nowadays some of the most common causes of visual impairment and blindness. Early diagnosis and appropriate treatment of these diseases can prevent visual loss. Usually, global visual impairment is 80% avoidable by early stage diagnosis . Population growth, aging and obesity are contributing factors to increase
Fig. 1. Anatomy of the human eye.
Fig. 2. Digital fundus image of the human eye.
Image of the interior surface of the eye is taken with the help of a fundus camera which consists of a microscope and camera. Fundus images are used for diagnosis of diseases.
Automated system with fundus image analysis helps to ophthalmologists by providing a second opinion. Concerning this aspect, optic disc (OD) segmentation is a key process in many algorithms designed for the automatic extraction of anatomical ocular structures, the detection of retinal lesions and identification of the...