- Glaucoma
- An eye condition in which the fluid pressure inside the eyes rises because of slowed fluid drainage from the eye. Untreated, it may damage the optic nerve and other parts of the eye, causing vision loss or even blindness. Two million Americans have glaucoma and every year 120,000 Americans go blind from the disease. The elderly, African-Americans, and people with family histories of the disease are at greatest risk. Glaucoma is often called "the sneak thief of sight." Often, by the time the patient notices vision loss, glaucoma can only be halted, not reversed. There are several different types of glaucoma, including open-angle glaucoma (the common adult-onset type of glaucoma) and acute angle-closure glaucoma (a less common form of glaucoma but one that can rapidly impair vision). The treatment of glaucoma may include medication, surgery, or laser surgery. Eyedrops or pills alone can usually control glaucoma, although they cannot cure it. Some drugs are designed to reduce pressure by slowing the flow of fluid into the eye, while others help to improve fluid drainage. These drugs may stop working over time or cause side effects, so your eye-care professional may select other drugs, change the dose, or use other means to deal with the glaucoma. Surgery to help fluid escape from the eye was once extensively used, but except for laser surgery, it is now reserved for the most difficult cases. In laser surgery for glaucoma, a laser beam of light is focused on the part of the anterior chamber where the fluid leaves the eye. This results in a series of small changes, making it easier for fluid to exit. Over time, the effect of laser surgery may wear off.
* * *A disease of the eye characterized by increased intraocular pressure, excavation, and atrophy of the optic nerve; produces defects in the field of vision. [G. glaukoma, opacity of the crystalline lens, fr. glaukos, bluish green]- angle-closure g. primary g. in which contact of the iris with the peripheral cornea excludes aqueous humor from the trabecular drainage meshwork. SYN: acute g., closed-angle g., narrow-angle g..- aphakic g. g. following cataract removal.- α-chymotrypsin-induced g. transient secondary g. following the use of α-chymotrypsin in cataract extraction.- combined g. g. with angle-closure and open-angle mechanisms in the same eye.- compensated g. SYN: open-angle g..- congenital g. SYN: buphthalmia.- corticosteroid-induced g. g. caused by a hereditary predisposition in which local instillation of eyedrops containing corticosteroid causes increased intraocular pressure.- ghost cell g. g. occurring after vitrectomy, arising from erythrocyte membranes blocking outflow channels of aqueous humor.- low-tension g. optic nerve atrophy and excavation with typical field defects of g. but without abnormal increase in intraocular pressure. SYN: normal-tension g..- malignant g. secondary g. caused by forward displacement of the iris and lens, obliterating the anterior chamber; usually follows a filtering operation for primary g..- neovascular g. g. occurring in rubeosis iridis.- normal-tension g. SYN: low-tension g..- open-angle g. primary g. in which the aqueous humor has free access to the trabecular meshwork. SYN: chronic g., compensated g., simple g., g. simplex.- phacogenic g. SYN: phacomorphic g..- phacolytic g. g. secondary to hypermature cataract and occlusion of the trabecular drainage meshwork by lens material.- phacomorphic g. secondary g. caused by either excessive size or spherical shape of the lens. SYN: phacogenic g..- pigmentary g. g. associated with erosion of pigment from the posterior iris, and with an accumulation of pigment particles in the trabecular meshwork.- pseudoexfoliative g. g. occurring in association with widespread deposition of cellular organelles on the lens capsule, ocular blood vessel s, iris, and ciliary body. SEE ALSO: pseudoexfoliation of lens capsule.- pupillary block g. g. secondary to failure of the aqueous humor to pass through the pupil to the anterior chamber.
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glau·co·ma glau̇-'kō-mə, glȯ- n a disease of the eye marked by increased pressure within the eyeball that can result in damage to the optic disk and gradual loss of vision* * *
n.a condition in which loss of vision occurs because of an abnormally high pressure in the eye. In most cases there is no other ocular disease. This is known as primary glaucoma and there are two pathologically distinct types: acute and chronic simple. In acute (or angle-closure) glaucoma, there is an abrupt rise in pressure due to sudden closure of the angle between the cornea and iris where aqueous humour usually drains from the eye. This is accompanied by pain and marked blurring of vision associated with inflammation of the anterior segment. In the more common chronic simple (or open-angle) glaucoma, the pressure increases gradually, usually without producing pain, and the visual loss is insidious. The same type of visual loss may rarely occur in eyes with a normal pressure: this is called low-tension glaucoma. Primary glaucoma occurs increasingly with age and is an important cause of blindness. Secondary glaucoma may occur when other ocular disease impairs the normal circulation of the aqueous humour and causes the intraocular pressure to rise.In all types of glaucoma the eventual problem is to reduce the intraocular pressure. Drops are inserted into the eye at regular intervals to improve the outflow of aqueous humour from the eye and/or to reduce the production of aqueous humour. Drugs used for this purpose include beta blockers (e.g. timolol, levobunolol, carteolol), carbonic anhydrase inhibitors (e.g. brinzolamide, dorzolamide), alpha-receptor stimulants (e.g. apraclonidine, brimonidine), and latanoprost. If this treatment is ineffective, surgery may be performed to make a new channel through which the aqueous humour may drain from the eye in sufficient quantities to allow the pressure to return to normal. Such operations are known as drainage or filtering operations.* * *
glau·co·ma (glaw-) (glou-koґmə) [Gr. glaukōma opacity of the crystalline lens (from the dull gray gleam of the affected eye)] a group of eye diseases usually characterized by an increase in intraocular pressure that causes pathologic changes in the optic disk and typical defects in the field of vision. glaucomatous adj
Medical dictionary. 2011.
