cataract

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cataract,

in medicine, opacity of the lens of the eye, which impairs vision. In the young, cataracts are generally congenital or hereditary; later they are usually the result of degenerative changes brought on by aging or systemic disease (diabetesdiabetes
or diabetes mellitus
, chronic disorder of glucose (sugar) metabolism caused by inadequate production or use of insulin, a hormone produced in specialized cells (beta cells in the islets of Langerhans) in the pancreas that allows the body to use and store
..... Click the link for more information.
). Cataracts brought on by aging are most common; most individuals over 60 exhibit some degree of lens opacity. Injury, extreme heat, ultraviolet light, X rays, nuclear radiation, inflammatory disease, and toxic substances also cause cataracts. There is growing concern that further disintegration of the ozone layerozone layer
or ozonosphere,
region of the stratosphere containing relatively high concentrations of ozone, located at altitudes of 12–30 mi (19–48 km) above the earth's surface.
..... Click the link for more information.
 will increase the incidence of cataracts. Advanced cataracts are usually treated by surgical removal of the lens and implantation of an artificial lens. After cataract surgery, which is the most common surgical procedure in the United States, most patients do not require thick glasses or contact lenses.
The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Cataract

 

an opacity of the crystalline lens of the eye that prevents light from penetrating into the eye and that results in decreased visual acuity. The term “cataract” reflects the mistaken conception of the ancient Greeks that a cataract is caused by the effusion of a turbid fluid between the iris and the lens. Cataracts are distinguished according to the location of the opacity in the lens: capsular (in the capsule covering the lens), cortical (in the peripheral layers of the lens), and nuclear (in its central layers).

Cataracts may be congenital or acquired. Congenital cataracts develop in the intrauterine period, and the opacity generally does not enlarge or change with age. In congenital cataracts, parts of the lens almost invariably remain transparent, and visual acuity is not completely impaired. Depending on the site of the opacities, cataracts may be anterior or posterior polar (limited opacities of the capsule of the lens), lamellar, and so forth.

Senile cataracts constitute most of the acquired cataracts, and they are characterized by progression of the opacities of the lens. In senile cataracts, opacities appear first in the periphery of the lens (incipient senile cataract), and vision remains unimpaired. The number of opacities then increases and they coalesce, resulting in a marked decrease in visual acuity (immature cataract). As the condition develops, all the layers of the lens become cloudy and it turns grayish white or mother-of-pearl; visual acuity decreases to photoperception—that is, the eye becomes virtually blind (mature senile cataract). Also acquired are complicated cataracts that arise in some systemic diseases (diabetes, cholera, digestive disorders) or result from diseases of the eye itself (inflammation of the uveal tract, progressive myopia). Cataracts resulting from eye injuries, effects of radiation, and so forth constitute a large group of acquired cataracts.

Treatment is generally surgical. In some cases it involves transplanting an artificial lens.

REFERENCE

Dymshits, L. A. “Bolezni khrustalika.” In Mnogotomnoe rukovodstvo po glaznym bolezniam, vol. 2, book 2. Moscow, 1960.

L. A. KATSNEL’SON

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

cataract

[′kad·ə‚rakt]
(hydrology)
A waterfall of considerable volume with the vertical fall concentrated in one sheer drop.
(medicine)
An opacity in the crystalline lens or the lens capsule of the eye.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

cataract

1. a large waterfall or rapids
2. Pathol
a. partial or total opacity of the crystalline lens of the eye
b. the opaque area
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
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Thus, our study provides a clear comparison of the effects of ECCE and phacoemulsification on the endothelial cell loss rate in post-PKP eyes with complicated cataract for the first time.
The study included 29 eyes of 22 adult aphakic patients who presented between 1990 and 2011 due to glaucoma following complicated cataract surgery.
Comparison of outcomes of primary anterior chamber versus secondary scleral-fixated intraocular lens implantation in complicated cataract surgeries.
Discussion: Complicated cataracts which may develop after PPV can be treated safely with phacoemulsificarion.
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EXCLUSION CRITERIA: Complicated cataract, traumatic cataract, corneal opacities, corneal degenerations, uveitis, pseudo exfoliation, glaucoma, connective tissue disorders, and previous ocular surgeries, pathological conditions of the optic nerve and retina, external eye diseases, uncontrolled diabetes, uncontrolled hypertension.