glaucoma glaucoma glaucoma 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) glaucoma, in which the drainage angle for fluid within the eye remains open, with less common types including closed-angle (narrow angle, acute congestive) glaucoma and normal-tension glaucoma. open-angle glaucoma develops slowly over time without pain. peripheral vision may begin to decrease, followed by central vision, resulting in blindness if not treated. closed-angle glaucoma 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 glaucoma, once it has occurred, is permanent. eyes affected by glaucoma are referred to as being glaucomatous. glaucomaacute angle closure glaucoma of a person's right eye (shown at left). note the mid-sized pupil, which is non-reactive to light, and redness of the white part of the eye.specialtyophthalmology, optometrysymptomsvision losseye painmid-dilated pupilredness of the eyenauseausual onsetgradual, or suddenrisk factorsincreased pressure in the eye, family history, high blood pressurediagnostic methoddilated eye examinationdifferential diagnosisuveitis, trauma, keratitis, conjunctivitistreatmentmedication, laser, surgeryfrequency6–67 million risk factors for glaucoma include increasing age, high pressure in the eye, a family history of glaucoma, and use of steroid medication. for eye pressures, a value of 21 mmhg or 2.8 kpa 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 glaucoma. the mechanism of open-angle glaucoma is believed to be the slow exit of aqueous humor through the trabecular meshwork, while in closed-angle glaucoma 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 glaucoma medication are available. laser treatments may be effective in both open-angle and closed-angle glaucoma. a number of types of glaucoma surgeries may be used in people who do not respond sufficiently to other measures. treatment of closed-angle glaucoma is a medical emergency. about 70 million people have glaucoma globally, with about two million patients in the united states. it is the leading cause of blindness in african americans. it occurs more commonly among older people, and closed-angle glaucoma is more common in women. glaucoma has been called the "silent thief of sight", because the loss of vision usually occurs slowly over a long period of time. worldwide, glaucoma is the second-leading cause of blindness after cataracts. cataracts caused 51% of blindness in 2010, while glaucoma caused 8%. the word "glaucoma" 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. signs and symptoms photo showing conjunctival vessels dilated at the corneal edge (ciliary flush, circumcorneal flush) and hazy cornea characteristic of acute angle closure glaucoma as open-angle glaucoma is usually painless with no symptoms early in the disease process, screening through regular eye exams is important. 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. the word is german, meaning "glaucoma flecks". causes a normal range of visionthe same view with advanced vision loss from glaucoma 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). dietary no clear evidence indicates that vitamin deficiencies cause glaucoma in humans. as such, oral vitamin supplementation is not a recommended treatment. caffeine increases intraocular pressure in those with glaucoma, but does not appear to affect normal individuals. ethnicity many people of east asian descent are prone to developing angle closure glaucoma because of shallower anterior chamber depths, with the majority of cases of glaucoma in this population consisting of some form of angle closure. higher rates of glaucoma have also been reported for inuit populations, compared to white populations, in canada and greenland. genetics positive family history is a risk factor for glaucoma. the relative risk of having primary open-angle glaucoma (poag) is increased about two- to four-fold for people who have a sibling with glaucoma. glaucoma, particularly primary open-angle glaucoma, is associated with mutations in several genes, including myoc, asb10, wdr36, ntf4, tbk1, and rpgrip1, although most cases of glaucoma do not involve these genetic mutations. normal-tension glaucoma, which comprises one-third of poag, is also associated with genetic mutations (including opa1 and optn genes). various rare congenital/genetic eye malformations are associated with glaucoma. occasionally, failure of the normal third-trimester gestational atrophy of the hyaloid canal and the tunica vasculosa lentis is associated with other anomalies. angle closure-induced ocular hypertension and glaucomatous optic neuropathy may also occur with these anomalies and has been modelled in mice. other laser doppler imaging reveals arterial blood flow reversal in neovascular glaucoma. the color change of the doppler image in the central retinal artery during the cardiac cycle indicates arterial flow reversal. other factors can cause glaucoma, known as "secondary glaucoma", including prolonged use of steroids (steroid-induced glaucoma); conditions that severely restrict blood flow to the eye, such as severe diabetic retinopathy and central retinal vein occlusion (neovascular glaucoma); ocular trauma (angle-recession glaucoma); and inflammation of the middle layer of the pigmented vascular eye structure (uveitis), known as uveitic glaucoma. pathophysiology human eye cross-sectional view the underlying cause of open-angle glaucoma remains unclear. several theories exist on its exact etiology. however, the major risk factor for most glaucomas and the focus of treatment is increased intraocular pressure. intraocular pressure is a function of production of liquid aqueous humor by the ciliary processes of the eye, and its drainage through the trabecular meshwork. aqueous humor flows from the ciliary processes into the posterior chamber, bounded posteriorly by the lens and the zonules of zinn, and anteriorly by the iris. it then flows through the pupil of the iris into the anterior chamber, bounded posteriorly by the iris and anteriorly by the cornea. from here, the trabecular meshwork drains aqueous humor via the scleral venous sinus (schlemm's canal) into scleral plexuses and general blood circulation. in open/wide-angle glaucoma, flow is reduced through the trabecular meshwork, due to the degeneration and obstruction of the trabecular meshwork, whose original function is to absorb the aqueous humor. loss of aqueous humor absorption leads to increased resistance and thus a chronic, painless buildup of pressure in the eye. in close/narrow-angle, the iridocorneal angle is completely closed because of forward displacement of the final roll and root of the iris against the cornea, resulting in the inability of the aqueous fluid to flow from the posterior to the anterior chamber and then out of the trabecular network. this accumulation of aqueous humor causes an acute increase in pressure and pain. degeneration of axons of the retinal ganglion cells (the optic nerve) is a hallmark of glaucoma. the inconsistent relationship of glaucomatous optic neuropathy with increased intraocular pressure has provoked hypotheses and studies on anatomic structure, eye development, nerve compression trauma, optic nerve blood flow, excitatory neurotransmitter, trophic factor, retinal ganglion cell/axon degeneration, glial support cell, immune system, aging mechanisms of neuron loss, and severing of the nerve fibers at the scleral edge. diagnosis optic nerve in advanced glaucoma disease screening for glaucoma is usually performed as part of a standard eye examination performed by optometrists and ophthalmologists. testing for glaucoma includes measurements of the intraocular pressure using tonometry, anterior chamber angle examination or gonioscopy as well as examination of the optic nerve to discern visible damage, changes in the cup-to-disc ratio, rim appearance and vascular change. a formal visual field test is performed. the retinal nerve fiber layer can be assessed with imaging techniques such as optical coherence tomography, scanning laser polarimetry or scanning laser ophthalmoscopy (heidelberg retinal tomogram). visual field loss is the most specific sign of the condition, though it occurs later in the course of the disease. as all methods of tonometry are sensitive to corneal thickness, methods such as goldmann tonometry may be augmented with pachymetry to measure the central corneal thickness (cct). a thicker cornea can result in a pressure reading higher than the true pressure but a thinner cornea can produce a pressure reading lower than the true pressure. because pressure-measurement error can be caused by more than just cct (such as by corneal hydration or elastic properties), it is impossible to adjust pressure measurements based only on cct measurements. the frequency-doubling illusion can also be used to detect glaucoma with the use of a frequency-doubling technology perimeter. examination for glaucoma is assessed with attention given to gender, race, history of drug use, refraction, inheritance and family history. glaucoma tests what the test examineseye drops usedphysical contact with the eyeprocedure tonometryinner eye pressuremaybemaybeeye drops may be used to numb the eye. the examiner then uses a tonometer to measure the inner pressure of the eye through pressure applied by a puff of warm air or a tiny tool. ophthalmoscopy (dilated eye examination)shape and color of the optic nerveyesnoeye drops are used to dilate the pupil. using a small magnification device with a light on the end, the examiner can examine the magnified optic nerve. perimetry (visual field test)complete field of visionnonothe patient looks straight ahead and is asked to indicate when light passes the patient's peripheral field of vision. this allows the examiner to map the patient's field of vision. gonioscopyangle in the eye where the iris meets the corneayesyeseye drops are used to numb the eye. a hand-held contact lens with a mirror is placed gently on the eye to allow the examiner to see the angle between the cornea and the iris. pachymetrythickness of the corneanoyesthe examiner places a pachymeter gently on the front of the eye to measure its thickness. nerve fiber analysisthickness of the nerve fiber layermaybemaybeusing one of several techniques, the nerve fibers are examined. glaucoma has been classified into specific types: primary glaucoma and its variants primary glaucoma (h40.1-h40.2) primary open-angle glaucoma, also known as chronic open-angle glaucoma, chronic simple glaucoma, glaucoma simplex high-tension glaucoma low-tension glaucoma primary angle closure glaucoma, also known as primary closed-angle glaucoma, narrow-angle glaucoma, pupil-block glaucoma, acute congestive glaucoma acute angle closure glaucoma (aka aacg) chronic angle closure glaucoma intermittent angle closure glaucoma superimposed on chronic open-angle closure glaucoma ("combined mechanism" – uncommon) variants of primary glaucoma pigmentary glaucoma exfoliation glaucoma, also known as pseudoexfoliative glaucoma or glaucoma capsulare primary juvenile glaucoma primary angle closure glaucoma is caused by contact between the iris and trabecular meshwork, which in turn obstructs outflow of the aqueous humor from the eye. this contact between iris and trabecular meshwork (tm) may