I. Introduction
Diabetic retinopathy is a common cause of visual loss and blindness in diabetic patients. Ophthalmologists play a most important role to help diabetic patients for an eye examination. However, the number of ophthalmologists is limited in Thailand. The study of Thailand diabetic project [1] shows that about one thousand ophthalmologists have to work with six million diabetic patients. Among all of them one million and a half of patients are effected by diabetic retinopathy. Therefore, automatic retinal image analysis is very essential to help ophthalmologists in detection and diagnosis of diabetic retinopathy. Exudates appear as bright lesions with the random yellowish deposits of varying size, shapes and location in retinal images. OD is known as the bright circular region which appears with similar features as exudates. Fig. 1 illustrates the position of OD and exudates in retinal image. OD and Exudates Region in Retinal Image