Alternative medicine can be used to achieve the healing effects of the experimental medicine, it also can predict diseases and prevent them, but validity of them is unproven. Iridology is an alternative medicine that claims to predict tissue weaknesses in the body by looking at the iris. The main object of this paper is to validate the using of iridology to predict diabetes, to do so iris images of 106 diabetic patients and 124 healthy controls were obtained and evaluated. The designed method is completely automatic and independent of iridologists. Also a novel algorithm is developed to improve the efficiency by finding the best region of iris automatically. The results showed the accuracy of 91.8% in the best setting, which shows the effectiveness of the proposed method.