Glaucoma is the second leading cause of blindness in the world. It is estimated that 66.8 million people in the world have glaucoma, with 6.7 million bilaterally blind from this disease. One of the glaucoma symptoms is that the cup enlarges until it occupies most of the disc area. This results in blindness. The cup-to-disc ratio is a measurement used in ophthalmology to detect glaucoma and assess its progression. This paper presents an approach to automatic calculation of cup to disc ratio using accurate detection of disc and cup, and quantitative determination of their areas in retinal fundus images to diagnose glaucoma. This method is computationally efficient. Experimental results indicate sufficient validity of the quantitative analysis to diagnose glaucoma.Keywords-Glaucoma; optic disc detection; optic cup detection, cup to disc ratio; retinal fundus image.