Cataract

For the band with this name, see Cataract (band). For the geographical features, see Cataracts of the Nile

Image:Eyesection.gif Image:Human eyesight two children and ball normal vision.jpg Image:Human eyesight two children and ball with cataract.jpg A cataract (origin is from Latin cataracta, a waterfall, and from Greek kataraktes, katarrhaktes, from katarassein, to dash down, from kata-, down + arassein, to strike, dash.) [1]is any opacitywhich develops in the crystalline lensof the eyeor in its envelope. Cataracts form for a variety of reasons, including long term ultraviolet exposure, secondary effects of diseases such as diabetes, or simply due to advanced age; they are usually a result of denaturationof lens proteins. Geneticfactors are often a cause of congenitalcataracts and may also play a role in predisposing someone to cataracts. Some cataract formation is to be expected in any person over the age of 70. Fully half of all people between the ages of 65 and 74 and about 70% of those over 75 have some cataract formation. Cataracts may also be produced by eye injuryor physical trauma. A study among Icelandairpilots showed commercial airline pilots as three times as likely to develop cataracts as people with non-flying jobs. This is thought to be caused by radiation coming from outer space.

Cataracts may be partial or complete, stationary or progressive, hard or soft.

Cataract surgery

Main article: Cataract surgery

An early technique to remove cataracts was couching, which involved using a thin needle or stick to remove the clouding. This technique is known to have existed in Roman times and continued to be used throughout the Middle Agesand continues to be used in underprivilleged "Third world" countries today. In India, however, modern surgery with intraocular lens insertion in Government and Non Government Organisation (NGO) sponsored Eye Surgical Camps have totally replaced this method.

The most effective and common treatment is cataract surgeryto remove the cloudy lens. There are two types of surgerythat can be used to remove cataracts, extra-capsular and intra-capsular surgery. Extra-capsular surgery consists of removing the lens but leaving the majority of the lens capsuleintact. High frequencysound waves(phacoemulsification) are sometimes used to break up the lens before extraction. Intra-capsular surgery involves removing the entire lens of the eye, including the lens capsule, but it is rarely performed in modern practice. In either extra-capsular surgery or intra-capsular surgery, the lens is replaced with a plasticlens (an intraocular lensimplant) which remains permanently in the eye.

Previously, polymethylmethacrylatewas used as the lens material. Advances have brought about the use of silicone acrylatewhich is a soft material. This allows the lens to be folded and inserted into the eye through a smaller incision. Acryliclenses can also be used with small incisions and are a better choice in people who have a history of uveitisor are at high risk of retinal detachment. Acrylic is not always an ideal choice due to its added expense.

Cataract operations are mostly performed under a local anaestheticand the patient will be allowed to go home the same day. Complications after cataract surgery are common. Many people (up to 50%) can develop a posterior capsular opacification after initial cataract surgery. This is a thickening and clouding of the lens capsule (which was left behind when the cataract was removed) and it can be easily corrected using a laserto make holes in the capsule for the person to see through. Retinal detachmentis an uncommon complication of cataract surgery.

Etymology

A cataract is a large waterfallor place where the flow of a riverchanges dramatically. The term comes from the Greekword kataraktes, whose meaning "to dash down" or "downrush" describes rapidly running water, and the Latin cataracta, whose meaning describes "a waterfall", "a floodgate", or "a portcullis". As rapidly running water turns white, the term was later used metaphorically to describe the similar appearance of mature ocular opacities.

Types of cataracts

• Classified by etiology

• Age-related cataract
• Congenital cataract
• Secondary cataract
• Traumatic cataract

• Classified by location

• Anterior cortical cataract
• Anterior polar cataract
• Anterior subcapsular cataract
• Nuclear cataract
• Posterior cortical cataract
• Posterior polar cataract
• Posterior subcapsular cataract

Humans with cataracts were accused of being possessed by Satan in the middle ages.

See also

• List of eye diseases and disorders

External links

• NHS Best Treatments Site
• eMedicine Health
• VisionSimulations.com | Images and vision simulators of various diseases and conditions of the eyede:Grauer Star

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It uses material from the http://en.wikipedia.org/wiki/Cataract Wikipedia article Cataract.