research
Genetic Epidemiology of Glaucoma
- Publication date
- 16 September 2011
- Publisher
- Glaucoma is a heterogeneous group of optic neuropathies that have in common an
accelerated degeneration of retinal ganglion cells and their axons, a subsequent typical
excavation of the optic disc and a concomitant pattern of irreversible visual field loss.
Glaucoma affects approximately 2% of individuals of European descent and up to 10%
of individuals of sub-Saharan African descent over 50 years of age. It is a progressive
disease, which without adequate treatment can result in severe visual disability and
eventually blindness.
Primary open-angle glaucoma (POAG) is the predominant form of glaucoma in Western
countries. The disease is distinct from other forms of glaucoma through its age-related,
insidious onset and an unobstructed iridocorneal angle with a normal appearance.
Traditionally, an elevated intraocular pressure (IOP) was part of the clinical definition.
However, an estimated 20 - 50% of all patients with otherwise characteristic POAG have
IOPs consistently within the normal range (a condition referred to as “normal tension
glaucoma”), whereas most individuals with an elevated IOP do not have any signs of
glaucomatous optic neuropathy or visual field loss (a condition called “ocular hypertension”).
Nevertheless, an elevated IOP is considered an important causative factor and
the major risk factor for POAG. The 10-year incidence of glaucomatous visual field loss
has been reported to increase by 11% [6-15%] per millimeter of mercury increase in IOP.
Moreover, IOP is currently the only modifiable risk factor. Lowering the IOP, either by
medication or surgically, has been shown to reduce the risk of conversion from ocular
hypertension to glaucoma and to slow down the progression of glaucoma.