- A clouding of the lens of the eye. The normally clear aspirin-sized lens of the eye starts to become cloudy. The result is much like smearing grease over the lens of a camera. It impairs normal vision. There are many causes of cataracts including cortisone medication, trauma, diabetes, many other diseases and simply aging. Cataracts will affect almost all people if they are fortunate enough to live long enough. The symptoms of cataracts include double or blurred vision and unusual sensitivity to light and glare. Cataracts can be diagnosed when the doctor examines the eyes with a viewing instrument. The ideal treatment for cataracts is surgical implantation of a new lens. Wearing sunglasses can help prevent cataracts.
* * *Complete or partial opacity of the ocular lens. SYN: cataracta. [L. cataracta, fr. G. katarrhaktes, a downrushing, a waterfall, fr. katarrhegnymi, to break down, rush down]- anular c. congenital c. in which a central white membrane replaces the nucleus. SYN: disk-shaped c., life-belt c., umbilicated c..- black c. a c. in which the lens is hardened and a dark brown. In the 19th century, German black c. meant gutta serena (q.v.). SYN: cataracta brunescens, cataracta nigra.- capsulolenticular c. a c. in which both the lens and its capsule are involved. SEE ALSO: membranous c..- cerulean c. [MIM*115660] a congenetal c. with bluish coloring and radial lesions; autosomal dominant inheritance in some cases.- complete c. SYN: mature c..- complicated c. SYN: secondary c. (1).- congenital c. c., usually bilateral, present at birth. It occurs as an autosomal recessive condition in calves of the Jersey breed. In humans approximately 25% of bilateral congenital cataracts are autosomal dominant [MIM*116200, *116700]; X-linked forms also exist [MIM*302200, *302300]. Most congenital cataracts are sporadic, some the result of prematurity, intrauterine infection, drug-related toxicity, injury, or chromosomal or metabolic disorders.- copper c. SYN: chalcosis lentis.- coralliform c. congenital c. with round or elongated processes radiating from the center of the lens.- coronary c. peripheral cortical developmental c. occurring just after puberty; transmitted as a hereditary dominant characteristic.- crystalline c. a hereditary c. with a coralliform or needle-shaped accumulation of crystals in the axial region of an otherwise clear lens.- cuneiform c. cortical c. in which the opacities radiate from the periphery like spokes of a wheel.- cupuliform c. a common form of senile c. often confined to a region just within the posterior capsule. SYN: saucer-shaped c..- disk-shaped c. SYN: anular c..- electric c. a c. caused by contact with a high-power electric current, or a lightning bolt. SYN: cataracta electrica.- embryonic c. [MIM*115650] a congenital c. situated near the anterior Y suture of the fetal lens nucleus. Inheritance heterogeneous.- fibroid c., fibrinous c. a sclerotic hardening of the capsule of the lens, following exudative iridocyclitis.- floriform c. a congenital c. with opacities arranged like the petals of a flower.- furnacemen's c. SYN: infrared c..- galactose c. a neonatal c. associated with intralenticular accumulation of galactose alcohol. See galactosemia.- glassworker's c. SYN: infrared c..- hard c. SYN: nuclear c..- hypermature c. a c. in which the lens cortex becomes liquid, with the nucleus gravitating within the capsule (Morgagni c.). SYN: overripe c..- infantile c. a c. affecting a very young child.- infrared c. a c. secondary to absorption of heat by the lens, or by transmission from the adjacent iris. SYN: furnacemen's c., glassworker's c..- juvenile c. a soft c. occurring in a child or young adult.- life-belt c. SYN: anular c..- membranous c. a secondary c. composed of the remains of the thickened capsule and degenerated lens fibers.- Morgagni c. a hypermature c. in which the nucleus gravitates within the capsule. SYN: sedimentary c..- overripe c. SYN: hypermature c..- perinuclear c. a lamellar c. in which the nucleus is clear but is surrounded by a ring of opacity.- pisciform c. a hereditary c. with bilateral fish-shaped opacities in the axial region of the fetal nucleus.- radiation c. a c. caused by excessive or prolonged exposure to ultraviolet rays, x-rays, radium, gamma rays, heat, or radioactive isotopes.- ripe c. SYN: mature c..- saucer-shaped c. SYN: cupuliform c..- secondary c. 1. a c. that accompanies or follows some other eye disease such as uveitis; SYN: complicated c.. 2. a c. occurring in the retained lens or capsule after a c. extraction.- sedimentary c. SYN: Morgagni c..- senile c. a c. occurring spontaneously in the elderly; mainly a cuneiform c., nuclear c., or posterior subcapsular c., alone or in combination.- siderotic c. a c. resulting from deposition of iron from an iron-containing intraocular foreign body.- spindle c. a c. in which the opacity is fusiform, extending from one pole to the other. SYN: fusiform c..- stationary c. a c. that does not progress.- stellate c. congenital c. with lens opacities radiating toward the periphery, with subcapsular and cortical changes.- sunflower c. SYN: chalcosis lentis.- sutural c. a congenital type of c. with opacities along the Y sutures of the fetal lens nucleus; usually does not affect vision.- toxic c. a c. caused by drugs or chemicals.- umbilicated c. SYN: anular c..- vascular c. congenital c. in which the degenerated lens is replaced with mesodermal tissue. SYN: cataracta adiposa, cataracta fibrosa.
* * *cat·a·ract 'kat-ə-.rakt n a clouding of the lens of the eye or its surrounding transparent membrane that obstructs the passage of light
* * *n.any opacity in the lens of the eye that results in blurred vision. Cataracts may be congenital or due to metabolic disease (such as diabetes), direct or indirect injury to the lens, or prolonged exposure of the eye to infrared rays (e.g. glass-blowers' cataract) or ionizing radiation, but they are most commonly a result of age (senile cataract). A type commonly related to ageing is nuclear sclerotic cataract, which results from increasing density and yellowing of the centre of the lens. A posterior subcapsular cataract, which develops at the rear surface of the lens within the lens capsule, is also related to ageing but occurs in addition with prolonged use of steroids and chronic ocular inflammation. Brunescent cataracts are dark brown and very dense, and a cortical cataract is one in which the opacity occurs in the soft outer part (cortex) of the lens. A Morgagnian cataract is a longstanding very opaque cataract in which the cortex has started to shrink and liquefy, leaving a central shrunken nucleus. Minor degrees of cataract do not necessarily impair vision seriously.Cataract is treated by removal of the affected lens (see cataract extraction, phacoemulsification); patients may wear a contact lens or appropriate spectacles to compensate for the missing lens but in modern practice a plastic intraocular lens implant is routinely placed inside the eye after surgery.
* * *cat·a·ract (katґə-rakt) [L. cataracta, from Gr. katarraktēs waterfall, portcullis (perhaps because an ocular opacity and a portcullis are obstructions)] a partial or complete opacity on or in the lens of the eye or its capsule, especially one impairing vision or causing blindness. Cataracts are classified by their morphology (size, shape, location) or etiology (cause or time of occurrence).
Medical dictionary. 2011.
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