<unk>  is a group of eye diseases that result in damage to the optic nerve (or retina) and cause vision loss. The most common type is open-angle (wide angle, chronic simple)<unk> , in which the drainage angle for fluid within the eye remains open, with less common types including closed-angle (narrow angle, acute congestive)<unk>  and normal-tension<unk> . Open-angle<unk>  develops slowly over time and there is no pain. Peripheral vision may begin to decrease, followed by central vision, resulting in blindness if not treated. Closed-angle<unk>  can present gradually or suddenly. The sudden presentation may involve severe eye pain, blurred vision, mid-dilated pupil, redness of the eye, and nausea. Vision loss from<unk> , once it has occurred, is permanent. Eyes affected by<unk>  are referred to as being<unk> tous. Risk factors for<unk>  include increasing age, high pressure in the eye, a family history of<unk> , and use of steroid medication. For eye pressures, a value of above atmospheric pressure (760 mmHg) is often used, with higher pressures leading to a greater risk. However, some may have high eye pressure for years and never develop damage. Conversely, optic nerve damage may occur with normal pressure, known as normal-tension<unk> . The mechanism of open-angle<unk>  is believed to be the slow exit of aqueous humor through the trabecular meshwork, while in closed-angle<unk>  the iris blocks the trabecular meshwork. Diagnosis is achieved by performing a dilated eye examination. Often, the optic nerve shows an abnormal amount of cupping. If treated early, it is possible to slow or stop the progression of disease with medication, laser treatment, or surgery. The goal of these treatments is to decrease eye pressure. A number of different classes of<unk>  medication are available. Laser treatments may be effective in both open-angle and closed-angle<unk> . A number of types of<unk>  surgeries may be used in people who do not respond sufficiently to other measures. Treatment of closed-angle<unk>  is a medical emergency. About 70 million people have<unk>  globally, with about two million patients in the United States. It occurs more commonly among older people, and closed-angle<unk>  is more common in women.<unk>  has been called the "silent thief of sight", because the loss of vision usually occurs slowly over a long period of time. Worldwide,<unk>  is the second-leading cause of blindness after cataracts. Cataracts caused 51% of blindness in 2010, while<unk>  caused 8%. The word<unk> " is from the Ancient Greek glaukos, which means "shimmering." In English, the word was used as early as 1587 but did not become commonly used until after 1850, when the development of the ophthalmoscope allowed doctors to see the optic nerve damage.
Glaucoma
Keratitis
Normal tension glaucoma
Conjunctivitis
Cat eye syndrome
Uveitis
Phacolytic glaucoma
Ocular hypertension