Glaucomatous optic neuropathy is classified by morphologic changes in the intrapapillary and parapapillary region of the optic nerve head and the retinal nerve fibre layer. These changes can be evaluated using descriptive optic nerve head variables which are the size and shape of the optic disc; size, shape and pallor of the neuroretinal rim; size of the optic cup in relation to the area of the disc; configuration and depth of the optic cup; cup-to-disc diameter ratio and cup-to-disc area ratio; position of the exit of the central retinal vessel trunk on the lamina cribrosa surface; presence and location of splinter-shaped haemorrhages; occurrence, size, configuration and location of parapapillary chorioretinal atrophy; diffuse and/or focal decrease of the diameter of the retinal arterioles; and visibility of the retinal nerve fibre layer. Assessment of these variables is useful for the early detection of glaucomatous optic nerve damage, to follow-up patients with glaucoma, to differentiate various types of the chronic open-angle glaucomas, and to get hints for the pathogenesis of glaucomatous optic nerve fibre loss.