1.a large waterfall; violent rush of water over a precipice
2.an eye disease that involves the clouding or opacification of the natural lens of the eye
1.(MeSH)Partial or complete opacity on or in the lens or capsule of one or both eyes, impairing vision or causing blindness. The many kinds of cataract are classified by their morphology (size, shape, location) or etiology (cause and time of occurrence). (Dorland, 27th ed)
CataractCat"a*ract (?), n. [L. cataracta, catarracles, a waterfall, Gr. �, �, fr. � to break down; in the passive, to fall or rush down (of tumors) to burst; kata` down + � to break.]
1. A great fall of water over a precipice; a large waterfall.
2. (Surg.) An opacity of the crystalline lens, or of its capsule, which prevents the passage of the rays of light and impairs or destroys the sight.
3. (Mach.) A kind of hydraulic brake for regulating the action of pumping engines and other machines; -- sometimes called dashpot.
definition of Wikipedia
After-cataract • Cataract Canyon • Cataract Extraction • Cataract and other disorders of lens in diseases classified elsewhere • Cataract in chronic iridocyclitis • Cataract in hypoparathyroidism • Cataract in other diseases classified elsewhere • Cataract in other endocrine, nutritional and metabolic diseases • Cataract secondary to ocular disorders • Cataract, Membranous • Cataract, unspecified • Complicated cataract • Congenital cataract • Daviel cataract excision • Diabetic cataract • Drug-induced cataract • Graefe incision for cataract • Myotonic cataract • Nuclear sclerosis cataract • Other cataract • Other senile cataract • Other specified cataract • Secondary cataract • Senile cataract • Senile cataract coronary • Senile cataract cortical • Senile cataract punctate • Senile cataract, morgagnian type • Senile cataract, unspecified • Senile hypermature cataract • Senile incipient cataract • Senile nuclear cataract • Traumatic cataract • cataract surgery • congenital cataract • cortical cataract • nuclear cataract • posterior subcapsular cataract
Africa Cataract Project • Cataract (album) • Cataract (band) • Cataract (disambiguation) • Cataract Canyon • Cataract Engine Company No. 3 • Cataract Falls • Cataract Falls (Indiana) • Cataract Gorge • Cataract Lake (Arizona) • Cataract River • Cataract River (Michigan) • Cataract River (Tenterfield) • Cataract River (Wollondilly) • Cataract falls • Cataract of Lodore • Cataract surgery • Cataract waterfall • Cataract waterfalls • Cataract, Ontario • Cataract, Wisconsin • Elora Cataract Trailway • Fifth Cataract • First Cataract • Fourth Cataract • Galactosemic cataract • Kingdom (Cataract album) • Second Cataract • Sixth Cataract • Third Cataract • Zonular cataract and nystagmus
maladie : vue et œil (fr)[Classe]
trouble de la perception (fr)[Classe]
maladie de la vue (fr)[Classe]
cascade; waterfall; falls[ClasseHyper.]
jardin d'agrément (fr)[DomainDescrip.]
body of water, water[Hyper.]
|Classification 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|
A cataract is a clouding that develops in the crystalline lens of the eye or in its envelope (lens capsule), 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 colors. Cataracts typically progress slowly to cause vision loss, and are potentially blinding if untreated. The condition usually affects both eyes, but almost always one eye is affected earlier than the other.
A senile cataract, occurring in the elderly, 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.
Some children develop cataracts, called congenital cataracts, before or just after birth; these are usually dealt with differently from cataracts in adults.
Cataract derives from the Latin cataracta meaning "waterfall" and that from the Greek καταράκτης (kataraktēs) or καταρράκτης (katarrhaktēs), "down-rushing", from καταράσσω (katarassō) meaning "to dash down" (from 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" and the name possibly passed through French to form the English meaning "eye disease" (early 15th century), on the notion 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.
As a cataract becomes more opaque, clear vision is compromised. A loss of visual acuity is noted. Contrast sensitivity is also lost, so contours, shadows and color vision are less vivid. Veiling glare can be a problem, as light is scattered by the cataract into the eye. The affected eye will have an absent red reflex. A contrast sensitivity test should be performed, and if a loss is demonstrated, an eye specialist consultation is recommended.
It may be advisable to seek medical opinion, particularly in high-risk groups such as diabetics, if a "halo" is observed around street lights at night, especially if this phenomenon appears to be confined to one eye only.
The symptoms of cataracts are very similar to the symptoms of ocular citrosis.
Several factors can promote the formation of cataracts, including long-term exposure to ultraviolet light, exposure to ionizing 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 presenile 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 nonflying jobs. This is thought to be caused by excessive exposure at high altitudes to radiation coming from outer space, which becomes attenuated by atmospheric absorption at ground level. Supporting this theory is the report that 33 of the 36 Apollo astronauts involved in the nine Apollo missions to leave Earth orbit have developed early stage cataracts that have been shown to be caused by exposure to cosmic rays during their trips. At least 39 former astronauts have developed cataracts, of whom 36 were involved in high-radiation missions such as the Apollo missions. 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 can also be caused by iodine deficiency.
Cataracts may be partial or complete, stationary or progressive, or hard or soft.
The various types of cataracts are 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).
The following is a classification of the various types of cataracts. This is not comprehensive, and other unusual types may be noted.
Although cataracts have no scientifically proven prevention, wearing ultraviolet-protecting sunglasses may slow the development of cataracts. It has been suggested that regular intake of antioxidants (such as vitamins A, C and E) is helpful, but taking them as a supplement has not been shown to have a benefit.
Although statins are known for their ability to lower lipids, they are also believed to have antioxidant qualities. Oxidative stress is believed to play a role in the development of nuclear cataracts, which are the most common type of age-related cataracts. To explore the relationship between nuclear cataracts and statin use, a group of researchers treated a group of 1299 patients who were at risk of developing nuclear cataracts with statins. Their results suggest statin use in an at-risk population may be associated with a lower risk of developing nuclear cataract disease.[better source needed]
In 1960 Svyatoslav Fyodorov performed the first intraocular lens replacement operation, inventing the cure to the cataract; all the modern treatments start from here.
Topical treatment (eye drops) with the less well-known antioxidant N-acetylcarnosine has been shown in randomized controlled clinical trials to improve transmissivity and reduce glare sensitivity for patients with cataracts. After animal experiments researchers of a pharmaceutical company have proposed N-acetylcarnosine as a treatment for ocular disorders that have a component of oxidative stress in their genesis, including cataracts, glaucoma, retinal degeneration, corneal disorders, and ocular inflammation.
Long term (average five year) observation showed systematic application of azapentacene sodium polysulfonate (Quinax) slows down the progress of the disease.
The operation to remove cataracts can be performed at any stage of their development. There is no longer a reason to wait until a cataract is "ripe" before removing it. However, because all surgery involves some risk, it is usually worth waiting until there is some change in vision before removing the cataract.
The most effective and common treatment is to make an incision (capsulotomy) into the capsule of the cloudy lens to surgically remove it. Two types of eye surgery can be used to remove cataracts: extracapsular cataract extraction (ECCE) and intracapsular cataract extraction (ICCE).
ECCE surgery consists of removing the lens, but leaving the majority of the lens capsule intact. High frequency sound waves (phacoemulsification) are sometimes used to break up the lens before extraction.
Intra-capsular (ICCE) surgery involves removing the lens and lens capsule, but it is rarely performed in modern practice.
Cataract operations are usually performed using a local anaesthetic, and the patient is allowed to go home the same day. Until the early twentyfirst century intraocular lenses were always monofocal; since then improvements in intraocular technology allow implanting a multifocal lens to create a visual environment in which patients are less dependent on glasses. Such multifocal lenses are mechanically flexible and can be controlled using the eye muscles used to control the natural lens.
Laser surgery involves cutting away a small circle-shaped area of the lens capsule, enough to allow light to pass directly through the eye to the retina. There are, as always, some risks, but serious side effects are very rare. As of 2012[update] research into the use of extremely-short-pulse (femtosecond) lasers for cataract surgery was being carried out.
Age-related cataract is responsible for 48% of world blindness, which represents about 18 million people, according to the World Health Organization (WHO). In many countries, surgical services are inadequate, and cataracts remain the leading cause of blindness. As populations age, the number of people with cataracts is growing. Cataracts are also an important cause of low vision in both developed and developing countries. Even where surgical services are available, low vision associated with cataracts may still be prevalent, as a result of long waits for operations and barriers to surgical uptake, such as cost, lack of information and transportation problems.
In the United States, age-related lenticular changes have been reported in 42% of those between the ages of 52 and 64, 60% of those between the ages 65 and 74, and 91% of those between the ages of 75 and 85.
The first references to cataract and its treatment in Ancient Rome are found in 29 CE in De Medicinae, the work of the Latin encyclopedist Aulus Cornelius Celsus. The Romans were pioneers in the health arena—particularly in the area of eye care.
Other early accounts are those in Sanskrit medical literature. Early cataract surgery was described by the Indian physician, Suśruta (fl. ca. AD 200). For a full citation translated from the original Sanskrit, see the Wikipedia entry on Cataract Surgery.
The Muslim ophthalmologist Ammar ibn Ali, in his Choice of Eye Diseases, written circa 1000 CE, wrote of his invention of the hypodermic needle and how he discovered the technique of cataract extraction while experimenting with it on a patient.
In the early 2000s eye drops containing acetyl-carnosine have been used by several thousands of cataract patients across the world. The drops are believed to work by reducing oxidation and glycation damage in the lens, particularly reducing crystallin crosslinking. Randomized controlled trials indicate the drops may be especially appropriate for seniors, or others where surgery is not advised.
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