after-cataract

cataract /cat·a·ract/ (-rakt) an opacity of the crystalline lens of the eye or its capsule.catarac´tous

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after-cataract  a recurrent capsular cataract.

atopic cataract  cataract in those with long-standing atopic dermatitis.

black cataract  see senile nuclear sclerotic c.

blue cataract , blue dot cataract blue punctate opacities scattered throughout the nucleus and cortex of the lens.

brown cataract , brunescent cataract see senile nuclear sclerotic c.

capsular cataract  one consisting of an opacity in the lens capsule.

complicated cataract  secondary c.

congenital cataract 

1. cataract present at birth, usually bilaterally; it may be mild or severe and may or may not impair vision depending on size, density, and location.

2. developmental c.

coronary cataract  tiny white opacities in a ring around the lens, the center and periphery of the lens remaining clear.

cortical cataract 

1. developmental punctate opacity common in the cortex and present in most lenses. The cataract is white or cerulean, increases in number with age, but rarely affects vision.

2. the most common senile cataract; white, wedgelike opacities are like spokes around the periphery of the cortex.

cupuliform cataract  a senile cataract in the posterior cortex of the lens just under the capsule.

developmental cataract  a type of small cataract in youth, resulting from heredity, malnutrition, toxicity, or inflammation, seldom affecting vision.

electric cataract  one occurring after an electric shock, especially to the head. Anterior subcapsular cataracts may form and develop within days; slowly developing or stationary opacities may follow a shock not to the head.

glassblowers' cataract , heat cataract posterior subcapsular opacities caused by chronic exposure to infrared (heat) radiation.

hypermature cataract  one with a swollen, milky cortex, the result of autolysis of the lens fibers of a mature cataract.

lamellar cataract  one affecting only certain layers between the cortex and nucleus of the lens.

mature cataract  one producing swelling and opacity of the entire lens.

membranous cataract  a condition in which the lens substance has shrunk, leaving remnants of the capsule and fibrous tissue formation.

morgagnian cataract  a mature cataract in which the cortex has liquefied and the nucleus moves freely within the lens.

nuclear cataract  one in which the opacity is in the central nucleus of the eye.

overripe cataract  hypermature c.

polar cataract  one at the center of the anterior (anterior polar c.) or posterior (posterior polar c.) pole of the lens.

pyramidal cataract  a conoid anterior cataract with its apex projecting forward into the aqueous humor.

radiation cataract  one caused by ionizing radiation, e.g., x-rays, or by nonionizing radiation, e.g., infrared (heat) rays, ultraviolet rays, microwaves.

ripe cataract  mature c.

secondary cataract  one resulting from disease, e.g., iridocyclitis; degeneration, e.g., chronic glaucoma, retinal detachment; or from surgery, e.g., glaucoma filtering, retinal reattachment.

senile cataract  cataract in the elderly.

senile nuclear sclerotic cataract  slowly increasing hardening of the nucleus, usually bilateral and brown or black, with the lens becoming inelastic and unable to accommodate.

snowflake cataract , snowstorm cataract one marked by gray or blue to white flaky opacities, seen in young diabetics.

total cataract  an opacity of all the fibers of a lens.

toxic cataract  that due to exposure to a toxic drug, e.g., naphthalene.

traumatic cataract  one due to injury to the eye.

zonular cataract  lamellar c.

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cataract [kat´ah-rakt]

opacity of the lens of the eye or its capsule. adj., adj catarac´tous.

Causes and Symptoms. Some cataracts result from injuries to the eye, exposure to great heat or radiation, or inherited factors. The great majority, however, are “senile” cataracts, which are apparently a part of the aging process of the human body.

Blurred and dimmed vision are often the first symptoms. The patient may find that a brighter reading light is needed, or objects must be held closer to the eyes for better vision. Continued clouding of the lens may cause double vision; eventually there may be a need for frequent changes of eyeglasses. These symptoms do not necessarily indicate cataract, but if any of them are present, an ophthalmologist should be consulted immediately.

Treatment. The only known effective treatment for cataract is surgical removal of the lens (lens extraction or cataract extraction). The procedure of choice was formerly intracapsular extraction, with total removal of the lens within its capsule. This may be done by forceps or by cryoextraction using a supercooled metal probe that forms a bond with the lens capsule. The inner portion of the lens can be removed by emulsification and aspiration. More recently the removed cataract has been replaced with a plastic intraocular lens. In this procedure the inner portions of the lens (the nucleus and cortex) may be all that is removed; the capsule is retained and the intraocular lens is placed inside it.

The lens of the eye serves only to focus light rays upon the retina. After cataract extraction the loss of the natural lens is compensated for by either special eyeglasses or contact lenses. Implantation of a permanent artificial lens, either during cataract surgery or later, is an alternative to use of cataract spectacles and a removable contact lens.

Patient Care. Eye drops are administered to produce mydriasis and vasoconstriction. Because these patients may have extremely poor eyesight, care should be taken that they do not injure themselves. (See also vision.) Local anesthesia is usually preferred for the surgical procedure and preoperative medications are given to produce drowsiness. Ambulatory care surgery with same-day admission and discharge is becoming increasingly routine. Careful observation of the patient on follow-up visits is important. One needs to be on the alert for a complaint of pain in the eye followed by nausea and vomiting. These could be signs that the patient has increased intraocular pressure within the operative eye and measures need to be taken to reduce the pressure.

after-cataract any membrane of the pupillary area after extraction or absorption of the lens. See also secondary cataract.

atopic cataract cataract occurring, most often in the second to third decade, in those with longstanding atopic dermatitis.

brown cataract (brunescent cataract) senile cataract appearing as a brown opacity.

capsular cataract one consisting of an opacity of the capsule of the lens.

complicated cataract secondary cataract.

cortical cataract an opacity in the cortex of the lens.

hypermature cataract one in which the entire lens capsule is wrinkled and the contents have become solid and shrunken, or soft and liquid.

immature cataract (incipient cataract) an incomplete cataract; the lens is only slightly opaque and the cortex clear.

intumescent cataract a mature cataract that progresses; the lens becomes swollen from the osmotic effect of degenerated lens protein, and this may lead to secondary angle closure (acute) glaucoma.

lenticular cataract opacity of the lens not affecting the capsule.

mature cataract a cataract that produces swelling and opacity of the entire lens; cataracts are removed before maturity.

presenile cataract a subcapsular senile cataract in a person under 40 years of age.

secondary cataract a cataract, usually posterior subcapsular, that arises from either disease (especially iridocyclitis), degeneration (such as chronic glaucoma or retinal detachment), or surgery (such as glaucoma filtering or retinal reattachment).

senile cataract cataract with no obvious cause occurring in persons over 50 years old.

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cataract

opacity of the lens of the eye or its capsule or both. Cataract may result from injuries to the eye, exposure to great heat or radiation, or inherited factors. Rare in cattle and swine, common in dogs. Treatment consists of surgical removal of the lens (lens extraction or cataract extraction). May affect the entire lens or be localized, e.g. posterior polar cataract.

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acquired cataract

any non-congenital cataract; usually the result of trauma, systemic disease or another eye disorder.

after-cataract

1. any membrane of the pupillary area after extraction or absorption of the lens.

2. secondary cataract (below).

capsular cataract

one consisting of an opacity of the capsule of the lens.

complicated cataract

a cataract occurring secondarily to other intraocular disease.

congenital cataract

present at birth; often not progressive. See also white eye calf syndrome.

cortical cataract

an opacity in the cortex of the lens. The common form of cataract in dogs; inherited in many breeds, often in association with progressive retinal atrophy.

developmental cataract

one that occurs at any age before the animal becomes an adult.

diabetic cataract

one associated with diabetes mellitus.

electric cataract

one caused by electrical current as in electrocution.

embryonal cataract

one caused by prenatal influences.

focal ring cataract

a perinuclear opacity with normal lens fibers surrounding it. Usually the result of an in utero or neonatal insult to the lens.

galactosemic cataract

see galactosemia.

hyaloid cataract

a focal opacity at the point where the hyaloid artery meets the posterior lens capsule. See also mittendorf's dot.

hypermature cataract

one in which the lens has begun to liquefy.

immature cataract

incomplete opacity.

incipient cataract

a very early stage of development with no impairment of vision.

inherited cataract

occurs in a number of breeds of cattle, often in combination with other abnormalities of the eye. Affected calves are usually normal in other respects and can be reared if the inconvenience of their blindness can be overcome. Also occurs in dogs, often with late onset and in association with other inherited ocular defects such as progressive retinal atrophy.

intumescent cataract

a mature cataract that has become swollen.

juvenile cataract

one developing in very young animals, for example dogs less than 6 months of age.

lenticular cataract

opacity of the lens not affecting the capsule.

mature cataract

one in which the lens is completely opaque.

morgagnian cataract

liquefaction, except the nucleus which drops to the bottom of the lens, and shrinkage of the capsule.

nuclear cataract

one involving the nucleus of the lens; the common form of congenital cataracts.

nuclear Y cataract

a form of congenital cataract in which small opacities outline the Y suture of the nucleus.

nutritional cataract

see galactosemia.

radiation cataract

one caused by radiation, as in radiotherapy.

reduplication cataract

a capsular opacity covered by another layer of epithelium.

secondary cataract

1. one that forms after most of the lens has been removed.

2. complicated cataract.

senile cataract

occurs in the aged of all species, preceded by nuclear sclerosis.

subcapsular cataract

may be anterior or posterior. Inherited in several breeds of dogs.

toxic cataract

one caused by exposure to a toxic substance.

traumatic cataract

one caused by trauma.

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after-cataract 

An opacity in the posterior capsule of the crystalline lens which may have remained or occurred after extracapsular cataract extraction (manual or phacoemulsification). Treatment is typically with a neodymium-yag laser to create a central hole in the capsule (capsulotomy). Syn. secondary cataract. See extracapsular cataract extraction.