The intraocular pressure can also have an effect, with higher pressures reducing the time until blindness. Epidemiology
As of 2010, there were 44.7 million people in the world with open angle glaucoma. The same year, there were 2.8 million people in the United States with open angle glaucoma. By 2020, the prevalence is projected to increase to 58.6 million worldwide and 3.4 million in the United States.Both internationally and in the United States, glaucoma is the second-leading cause of blindness. Globally, cataracts are a more common cause. Glaucoma is also the leading cause of blindness in African Americans, who have higher rates of primary open-angle glaucoma. Bilateral vision loss can negatively affect mobility and interfere with driving.A meta-analysis published in 2009 found that people with primary open angle glaucoma do not have increased mortality rates, or increased risk of cardiovascular death. History
The association of elevated intraocular pressure (IOP) and glaucoma was first described by Englishman Richard Banister in 1622: "...that the Eye be grown more solid and hard, then naturally it should be...". Angle-closure glaucoma was treated with cataract extraction by John Collins Warren in Boston as early as 1806. The invention of the ophthalmoscope by Hermann Helmholtz in 1851 enabled ophthalmologists for the first time to identify the pathological hallmark of glaucoma, the excavation of the optic nerve head due to retinal ganglion cell loss. The first reliable instrument to measure intraocular pressure was invented by Norwegian ophthalmologist Hjalmar August Schiøtz in 1905.
The only signs are gradually progressive visual field loss and optic nerve changes (increased cup-to-disc ratio on fundoscopic examination). About 10% of people with closed angles present with acute angle closure characterized by sudden ocular pain, seeing halos around lights, red eye, very high intraocular pressure (>30 mmHg (4.0 kPa)), nausea and vomiting, suddenly decreased vision, and a fixed, mid-dilated pupil. It is also associated with an oval pupil in some cases. Acute angle closure is an emergency. Opaque specks may occur in the lens in glaucoma, known as glaukomflecken. Causes
Ocular hypertension (increased pressure within the eye) is the most important risk factor for glaucoma, but only about 50% of people with primary open-angle glaucoma actually have elevated ocular pressure. Ocular hypertension—an intraocular pressure above the traditional threshold of 21 mmHg (2.8 kPa) or even above 24 mmHg (3.2 kPa)—is not necessarily a pathological condition, but it increases the risk of developing glaucoma. One study found a conversion rate of 18% within five years, meaning fewer than one in five people with elevated intraocular pressure will develop glaucomatous visual field loss over that period of time. It is a matter of debate whether every person with an elevated intraocular pressure should receive glaucoma therapy; currently, most ophthalmologists favor treatment of those with additional risk factors.Open-angle glaucoma accounts for 90% of glaucoma cases in the United States. Closed-angle glaucoma accounts for fewer than 10% of glaucoma cases in the United States, but as many as half of glaucoma cases in other nations (particularly East Asian countries).