System Development for Measuring the Arterious Venous Rate (AVR) for the Diagnosis of Hypertensive Retinopathy

The retinal blood vessels are very sensitive to the changes in the blood pressure. The changes in diameter of retinal vessels are an important sign of diseases such as hypertension, arteriosclerosis and diabetes, and may be used for the prevention of further consequences caused by the hypertension such as heart attack, brain stroke and renal failure. Those changes are reflected as arteriolar narrowing which changes the vessel caliber, and modify the arterious venous rate (AVR). Obtaining precise measurements of vascular widths is a critical and demanding process in automated retinal image analysis. A prototype system is developed for measuring the vessels caliber, calculates the AVR and determines the presence of Hypertensive Retinopathy. The process is implemented using different techniques of image and signal analysis including Gabor wavelet, gradients, morphological operations and Niblack. A classification algorithm is also implemented to separate veins from arteries. The diameter measurement is based on the image skeleton and the perpendicular segment of the vessel. The results obtained are presented.