Glaucoma is the second leading cause of legal blindness. It causes blindness in nearly 12,000 americans annually. Glaucoma is an optic neuropathy which is characterized by a specific pattern of optic nerve head and visual field damage. In some cases, the damage may be attributed to the increased intra-ocular pressure. However, in other instances, the underlying basis for the continuous damage to the optic nerve is not clear.

Glaucoma is divided into two broad types - Open angle and Angle closure. Each of these types of glaucoma, is then divided into primary and secondary forms. In the open-angle glaucomas, the eye is anatomically normal, however, the blockage or malfunction of the system that drains the fluid from the eye (the trabecular meshwork) leads to an elevated intra-ocular pressure. In glaucoma with a low tension, the abnormality is not at the level of the meshwork, rather, resides at the level of the optic disc. In the angle-closure glaucomas, the blockage of the drainage of fluid (aqueous humor) from the eye is due to the pressure inserted on the trabecular meshwork by the iris. The trabecular meshwork in this condition is normal.

Primary type of the open angle glaucoma is likely to be due to a heterogeneous group of disorders that is induced due to the interaction of multiple genes and environmental factors. In the January 31 issue of Science, Stone et al, report on the identification of a gene linked to open angle glaucoma. Sequence tagged site (STS) and haplotype sharing between families who had chromosome 1q-linked open angle glaucoma were used to identify the gene. The search led to the identification of mutations in a gene that encodes for a trabecular meshwork protein (TIGR). Three separate mutations (Gly35Val, Gln361STOP, Tyr430His) were found to be present in 4.4% of patients with familial glaucoma, and in 3.9% of unselected patients with glaucoma. The same mutations were found only in 0.3% of the general population and none in the normal volunteers. It is proposed that the product of TIGR may lead to an increased intra-ocular pressure by the obstruction of the aqueous outflow. The findings should facilitate developing accurate, inexpensive pre-symptomatic testing for identification of patients at risk of the disease.

REFERENCE:

Stone, E. M.; Fingert, J. H.; Alward, W. L. M.; Nguyen, T. D.; Polansky, J. R.; Sunden, S. L. F.; Nishimura, D.; Clark, A. F.; Nystuen, A.; Nichols, B. E.; Mackey, D. A.; Ritch, R.; Kalenak, J. W.; Craven, E. R.; Sheffield, V. C.: Identification of a gene that causes primary open angle glaucoma. Science 275: 668-670, 1997

RESOURCES:

Directory of Eye Care Professionals
Glaucoma FAQ
Glaucoma Research Foundation
International Glaucoma Association
Glaucoma Risk Chart
The Foundation Fighting Blindness
Eyeville Educational tools primarily for optometrists, ophthalmologists and eyecare professionals.
The Amercian Academy of Opththalmology
National Eye Institute
Joint Commission on Allied Health Personnel in Ophthalmology(JCAHPO)

CLINICAL SYNOPSIS:

137750; Glaucoma 1. Open angle; GLC1A
137760; Glaucoma 1. Open angle; GLC1B

DATABASE LINKS:

Glaucoma, Primary open angle, juvenile onset; JOAG glaucoma, hereditary juvenile

Gene Map Locus: 1q21-q31

Glaucoma 1, open angle, B; GLC1B

Gene Map Locus: 2cen-q13