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For other uses, see Cataract (disambiguation).
CataractClassification and external resources
Magnified view of cataract in human eye, seen on examination with a slit lamp using diffuse illumination
ICD-10
H25.-H26., H28., Q12.0
ICD-9
366
DiseasesDB
2179
MedlinePlus
001001
Human eye cross-sectional view, showing position of human lens. Courtesy NIH National Eye Institute
A cataract is a clouding that develops in the crystalline lens of the eye or in its envelope, varying in degree from slight to complete opacity and obstructing the passage of light. Early in the development of age-related cataract the power of the lens may be increased, causing near-sightedness (myopia), and the gradual yellowing and opacification of the lens may reduce the perception of blue colours. Cataracts typically progress slowly to cause vision loss and are potentially blinding if untreated. The condition usually affects both the eyes, but almost always one eye is affected earlier than the other.
A senile cataract, occurring in the aged, is characterized by an initial opacity in the lens, subsequent swelling of the lens and final shrinkage with complete loss of transparency. Moreover, with time the cataract cortex liquefies to form a milky white fluid in a Morgagnian cataract, which can cause severe inflammation if the lens capsule ruptures and leaks. Untreated, the cataract can cause phacomorphic glaucoma. Very advanced cataracts with weak zonules are liable to dislocation anteriorly or posteriorly. Such spontaneous posterior dislocations (akin to the historical surgical procedure of couching) in ancient times were regarded as a blessing from the heavens, because some perception of light was restored in the cataractous patients.
Cataract derives from the Latin cataracta meaning "waterfall" and the Greek kataraktes and katarrhaktes, from katarassein meaning "to dash down" (kata-, "down"; arassein, "to strike, dash"). As rapidly running water turns white, the term may later have been used metaphorically to describe the similar appearance of mature ocular opacities. In Latin, cataracta had the alternate meaning "portcullis", so it is also possible that the name came about through the sense of "obstruction". Early Persian physicians called the term nazul-i-ah, or 'descent of the water' - vulgarised into waterfall disease or cataract - believing such blindness to be caused by an outpouring of corrupt humour into the eye. In dialect English a cataract is called a pearl, as in "pearl eye" and "pearl-eyed".
Contents
1 Causes
2 Symptoms
3 Epidemiology
4 Cataract surgery
5 Prevention
6 Recent research
7 Types of cataracts
8 Associations with systemic conditions
9 See also
10 References and notes
11 External links
//
Causes
Cataracts develop from a variety of reasons, including long-term exposure to ultraviolet light, exposure to radiation, secondary effects of diseases such as diabetes, hypertension and advanced age, or trauma (possibly much earlier); they are usually a result of denaturation of lens protein. Genetic factors are often a cause of congenital cataracts and positive family history may also play a role in predisposing someone to cataracts at an earlier age, a phenomenon of "anticipation" in pre-senile cataracts. Cataracts may also be produced by eye injury or physical trauma. A study among Icelandair pilots showed commercial airline pilots are three times more likely to develop cataracts than people with non-flying jobs. This is thought to be caused by excessive exposure to radiation coming from outer space. Cataracts are also unusually common in persons exposed to infrared radiation, such as glassblowers who suffer from "exfoliation syndrome". Exposure to microwave radiation can cause cataracts. Atopic or allergic conditions are also known to quicken the progression of cataracts, especially in children.
Cataracts may be partial or complete, stationary or progressive, hard or soft.
Some drugs can induce cataract development, such as corticosteroids and Ezetimibe[citation needed] and Seroquel.
There are various types of cataracts, e.g. nuclear, cortical, mature, and hypermature. Cataracts are also classified by their location, e.g. posterior (classically due to steroid use) and anterior (common (senile) cataract related to aging).
Symptoms
As a cataract becomes more opaque, clear vision is compromised. A loss of visual acuity is noted. Contrast sensitivity is also lost, so that contours, shadows and color vision are less vivid. Veiling glare can be a problem as light is scattered by the cataract into the eye. A contrast sensitivity test should be performed and if a loss in contrast sensitivity is demonstrated an eye specialist consultation is recommended.
In the developed world, particularly...(and so on)
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