cataract

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cataract,

in medicine, opacity of the lens of the eye, which impairs vision. In the young, cataracts are generally congenital or hereditary; later they are usually the result of degenerative changes brought on by aging or systemic disease (diabetesdiabetes
or diabetes mellitus
, chronic disorder of glucose (sugar) metabolism caused by inadequate production or use of insulin, a hormone produced in specialized cells (beta cells in the islets of Langerhans) in the pancreas that allows the body to use and store
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). Cataracts brought on by aging are most common; most individuals over 60 exhibit some degree of lens opacity. Injury, extreme heat, ultraviolet light, X rays, nuclear radiation, inflammatory disease, and toxic substances also cause cataracts. There is growing concern that further disintegration of the ozone layerozone layer
or ozonosphere,
region of the stratosphere containing relatively high concentrations of ozone, located at altitudes of 12–30 mi (19–48 km) above the earth's surface.
..... Click the link for more information.
 will increase the incidence of cataracts. Advanced cataracts are usually treated by surgical removal of the lens and implantation of an artificial lens. After cataract surgery, which is the most common surgical procedure in the United States, most patients do not require thick glasses or contact lenses.

Cataract

 

an opacity of the crystalline lens of the eye that prevents light from penetrating into the eye and that results in decreased visual acuity. The term “cataract” reflects the mistaken conception of the ancient Greeks that a cataract is caused by the effusion of a turbid fluid between the iris and the lens. Cataracts are distinguished according to the location of the opacity in the lens: capsular (in the capsule covering the lens), cortical (in the peripheral layers of the lens), and nuclear (in its central layers).

Cataracts may be congenital or acquired. Congenital cataracts develop in the intrauterine period, and the opacity generally does not enlarge or change with age. In congenital cataracts, parts of the lens almost invariably remain transparent, and visual acuity is not completely impaired. Depending on the site of the opacities, cataracts may be anterior or posterior polar (limited opacities of the capsule of the lens), lamellar, and so forth.

Senile cataracts constitute most of the acquired cataracts, and they are characterized by progression of the opacities of the lens. In senile cataracts, opacities appear first in the periphery of the lens (incipient senile cataract), and vision remains unimpaired. The number of opacities then increases and they coalesce, resulting in a marked decrease in visual acuity (immature cataract). As the condition develops, all the layers of the lens become cloudy and it turns grayish white or mother-of-pearl; visual acuity decreases to photoperception—that is, the eye becomes virtually blind (mature senile cataract). Also acquired are complicated cataracts that arise in some systemic diseases (diabetes, cholera, digestive disorders) or result from diseases of the eye itself (inflammation of the uveal tract, progressive myopia). Cataracts resulting from eye injuries, effects of radiation, and so forth constitute a large group of acquired cataracts.

Treatment is generally surgical. In some cases it involves transplanting an artificial lens.

REFERENCE

Dymshits, L. A. “Bolezni khrustalika.” In Mnogotomnoe rukovodstvo po glaznym bolezniam, vol. 2, book 2. Moscow, 1960.

L. A. KATSNEL’SON

cataract

[′kad·ə‚rakt]
(hydrology)
A waterfall of considerable volume with the vertical fall concentrated in one sheer drop.
(medicine)
An opacity in the crystalline lens or the lens capsule of the eye.

cataract

1. a large waterfall or rapids
2. Pathol
a. partial or total opacity of the crystalline lens of the eye
b. the opaque area
References in periodicals archive ?
Furthermore, several other metabolic pathways such as oxidative stress, activation of mitogen-activated protein kinase and cyclooxygenase-2, accumulation of cytosolic calcium, activation of NF-[kappa]B, and activation of protein-1, which all relate to polyol pathway but signal through distinct mechanisms, were found important for the development of diabetic cataract [26-28].
In addition to this, a recent case report describes a patient with early diabetic cataract and an onset of monogenic-type diabetes caused by a mutation within the insulin gene (INS), which until now, has not been associated with diabetic cataract [31].
Effects of N-acetylcysteine and glutathione ethyl ester drops on streptozotocin-induced diabetic cataract in rats.
Curcumin and turmeric delay streptozotocin-induced diabetic cataract in rats.
These data indicated that administration of rHV3 eye drops might dose-dependently inhibit the development of STZ induced diabetic cataract, and the effect was significantly more pronounced than that with pirenoxine sodium eye drops treatment.
The lens MDA levels in untreated cataractous group (group B) were significantly increased as compared to the normal control (group A), which implied the increased lipid peroxidation in the lens due to STZ-induced diabetic cataract. However, the MDA levels in groups C, D, E were significantly decreased with rHV3 drops treatment as compared to group B, and there were statistically significant differences between groups B and E (P < 0.01) and groups B and D (P < 0.05) Table 4).
Therefore, it has been considered as the potential therapeutic target for both diabetic cataract and diabetic retinopathy [22, 35].
Interestingly, diabetic rats which received MPO at all doses used in this study showed the reduction of aldose reductase activity and the expression of both p38MAPK and ERK1/2 in rat lens together with the improved both diabetic cataract and diabetic retinopathy.
We expect that dysregulations of the above genes can provide some information for rational development of drugs against galactosemic or diabetic cataract.
So, daily diet rich of diosgenin such as Dioscorea nipponica Makino, Dioscorea zingiberensis, Dioscorea bulbifera, Dioscorea oppositifolia, and common yam rhizome is recommended to diabetic subjects to postpone the onset of diabetic cataract, because a delay of cataract onset by 10 years can reduce the need for cataract surgery by as much as half [24].
These findings warrant investigations on the potential of L-carnosine as a therapeutic agent for delaying the development of diabetic cataract by mopping up excess glucose in the aqueous humour without deleterious effects on lens crystallins.
Chung, "Contributions of polyol pathway to oxidative stress in diabetic cataract," The FASEB Journal, vol.