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
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). 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 ?
Role of preoperative B-scan to detect posterior segment pathologies in eyes with age related mature cataract.
The purpose of the study is to visualize the status of posterior segment of eye with the diagnostic tool of B-scan ultrasound and to find out any posterior segment lesions are present in mature and hyper mature cataracts where fundus cannot be evaluated with other means.
published an article (AL-Shifa Journal of Ophthalmology 2007; 3(2):61-66 Pakistan), in 2003 studied on B-Scan USG in 209 eyes with age related mature cataract and found 29 (13.
The first patient was an Iraqi woman with dense mature cataracts in both eyes.
The first patient was an Iraqi woman with dense mature cataracts in both eyes; a bilateral cataract surgery was performed successfully by specialist consultants at the hospital at Dubai Health Care City.
Undergraduate Matthew Chart told OT how the students witnessed a wide range of interesting cases including mature cataracts, periorbital cellulites and advanced diabetic retinopathy.
The oldest patient treated at the camp was a 98-year-old man with mature cataracts, whose vision had been reduced to light perception only; the youngest was a 14-year-old boy with congenital cataracts and severe vision deterioration.
Further, for the more advanced and mature cataracts, which is common in the Indian population, performing phacoemulsification becomes more difficult and complication prone, finally one has to spend 200-600 $ or more for this surgery.
Of the cortical type, 428 were immature and 168 mature cataracts.