cataract

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Related to cataractous: intumescent cataract, brunescent cataract

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.

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

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.

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
References in periodicals archive ?
As with glutathione, levels of SOD decrease in human lenses with senile cataracts as the cataract advances; moreover, glutathione levels are positively correlated with SOD activity in the human cataractous lens.
The impairment of cataractous vision was selected for investigation for two primary reasons: (a) cataractous vision is an extremely common disorder that affects all (or nearly all) individuals as part of the aging process (e.
Moreover, Catalys' proprietary lens fragmentation capability has been shown to reduce the amount of effective phacoemulsification time needed to remove the cataractous lens by up to 96 percent, providing a gentler and potentially safer procedure for patients and an enhanced experience for surgeons.
Results of intraocular lens implantation with capsular tension ring in subluxated crystalline or cataractous lenses in children.
8) Moreover, researchers examining cataractous human lens nuclei found an inverse relationship between vitamin C concentration in the lens and cataract severity.
Features of other (uninvolved) ocular tissues (1) Cornea (eg, clear, cloudy, opaque) (2) Anterior chamber (eg, deep, shallow, flat) (3) Angle (eg, open, narrow, closed) (4) Iris (eg, color, any abnormalities) (5) Ciliary body (6) Lens (eg, clear, cataractous, presence of lens implant, absence) (7) Vitreous (eg, color, consistency, hemorrhage) (8) Retina (eg, detachment, total or partial; hemorrhages) (9) Choroid (10) Sclera (eg, thinning, defects) (11) Optic disc (eg, pallor, increased cup/ disc ratio) 3.
Previous studies examined the effect of artificial restriction of the binocular visual field and also of frosted lenses, which simulated mild cataractous changes (Wood & Troutbeck, 1994).
Moreover, Catalys has been shown to reduce the amount of ultrasound energy needed to remove the hard cataractous lens by up to 96 percent, providing a gentler and potentially safer procedure for patients and an enhanced experience for surgeons.
A study of chromium in human cataractous lenses and whole blood of diabetics, senile, and normal population.
2) published their finding of a highly statistical significant relationship between opalescent quality and color of lens nucleus on the mechanical compression character of cataractous lens.
In this study, our aim was to evaluate anterior segment biometry using OLCR and corneal endothelial changes with confocal microscopy in PEX syndrome/glaucoma eyes before cataract surgery and compare these findings with cataractous eyes without PEX syndrome.
ly/1DmEXyD), shows that treating cataractous lenses with lanosterol, a molecular building block of steroids, was found to reduce the cloudy protein build up in the tissue.