INTRODUCTIONGlaucoma is a heterogeneous group of disorders and is the most common cause of irreversible blindness worldwide. Glaucoma is defined by the progressive loss of retinal ganglion cells and is associated with characteristic optic neuropathy and visual field loss. Most forms of glaucoma are felt to have a significant genetic susceptibility. A number of genes and chromosomal loci have been identified through genetic linkage or association analysis that are associated with or, in rare cases, causative for different types of glaucoma. Genome-wide approaches are improving our understanding of the genetic basis of glaucoma. What follows is a comprehensive discussion of the role of genetics in those types of glaucoma in which the genetic contribution to the disease is better understood; this includes primary open-angle glaucoma (POAG), exfoliation glaucoma (XFG), primary congenital glaucoma (PCG), and developmental glaucoma.Glaucoma is a disease known since the Hippocrates time. This term indicates a number of neurodegenerative diseases having in common a progressive optical atrophy resulting from the apoptosis of retinal ganglion cells, axon atrophy, and degeneration extending to the visual areas of the brain cortex, finally leading to the characteristic optical-cup neuropathy and to irreversible visual loss. The action of many factors including ageing, genetic predisposition, and exogenous environmental and endogenous factors, is necessary for glaucoma development. In addition to ganglion cell loss, most glaucoma types are characterized by high intraocular pressure. This is due to the damage occurring in the trabecular meshwork, a key region in the pathogenesis of high-pressure glaucoma. In normal-pressure glaucoma, pathogenesis is different from vascular factors playing a remarkably important role.