OMIM ID:
Glaucoma, Open Angle, Primary
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
It has long been known from both clinical and genetic criteria that the disease called glaucoma is a heterogeneous condition. The common denominator is considered to be an optic neuropathy for which the primary risk factor is an elevation of intraocular pressure. However, the well-known clinical profile of glaucomatous retinal and optic nerve damage can also be found among patients without increased IOP and for these the cause remains elusive. Ultimately, damage to retinal neurons and their axons result in loss of visual field and optic nerve volume with eventual blindness if untreated.
Systemic Features
No systemic abnormalities are consistently associated with primary open angle glaucoma. However, glaucoma occurs in a large number of ocular and systemic disorders as well as chromosomal aberrations and in many such conditions there are anatomic abnormalities in the anterior chamber angle. A variety of mainly anecdotal risk factors such as obesity, smoking, diabetes, migraines, stress and cardiovascular disease have been reported but their causative relationships have not been established.
Genetics
Inheritance
Primary open angle glaucoma likely consists of a collection of disorders resulting from an optic neuropathy. Based on family data and ethnic distribution there can be little doubt that genes influence susceptibility to this disease. In fact, 13 types have been described based on the unique chromosomal locations of mutations that have been associated with each. Mutations in MYOC (1q23-q24) are responsible for a substantial proportion of POAG cases known as GLC1A through as yet unknown mechanisms. Others types labeled GLC1B through GLC1O may result from specific mutations located on 10 different chromosomes. In the absence of pedigrees with typical Mendelian inheritance patterns, it is reasonable to consider that the genes reported to be associated with POAG so far simply confer susceptibility to the optic neuropathy characteristic of clinical glaucoma (for further discussion see 137760). Unidentified environmental factors in combination with other genes in individual genomes likely determine the degree of susceptibility in each person.