The changes in diameter of retinal vessels are an important sign of diseases such as hypertension, arteriosclerosis and diabetes. Obtaining precise measurements of vascular widths is a critical and demanding process in automated retinal image analysis. This paper presents the development of a prototype for measuring the vessel diameters to calculate the arteriovenous ratio (AVR) by using different techniques including Gabor wavelet, gradients, morphological operations and Niblack. The diameter measurement is based on the image skeleton and the perpendicular segment of the vessel. An executable tool is developed using MATLAB and the results are evaluated.