Although glaucoma is a major global cause of blindness, the lack of a uniform definition of the disease in its different forms makes it difficult to assess its public health impact. By considering the common features of glaucoma, we have analysed available data on the three main forms of the disease: congenital/hereditary glaucoma, primary open-angle, and primary angle-closure glaucoma. A simple model was then developed to estimate the extent of glaucoma on a regional basis, taking into account demographic data, e.g., age distribution, gender and ethnic groups. Overall, the results demonstrate that glaucoma is responsible for approximately 5.2 million blind (15% of the total burden of world blindness).