Eye diseases. Cataract (most important)

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Eye diseases. Cataract (most important)

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52. Cataract

Cataract - partial or complete clouding of the substance or capsule of the lens with a decrease in visual acuity up to its complete loss. There are primary and secondary cataracts, acquired and congenital. Congenital cataracts can be hereditary or result from intrauterine developmental disorders, such as infections in the mother, such as rubella, etc.

Depending on the etiological factor, several groups of cataracts are distinguished: senile, traumatic, complicated, radiation, toxic and metabolic.

Complicated cataracts often form against the background of chronic uveitis of various origins due to the toxic effects of inflammatory products on the lens.

The lens is very sensitive to radiation exposure: infrared radiation, which causes damage to the anterior lens capsule in the form of peeling of the surface layers, ultraviolet radiation (290329 nm), ionizing radiation.

As a result of exposure to a number of chemicals (naphthalene, dinitrophenol, thallium, mercury, ergot), toxic cataracts develop. The entry of alkali into the conjunctival cavity causes damage to the conjunctiva, cornea and iris and often leads to the development of cataracts. Cataracts occur in certain metabolic diseases: diabetes mellitus, galactosemia, hypocalcemia, Westphal-Wilson-Konovalov disease, myotonic dystrophy, protein starvation.

In diabetes mellitus, with an increase in blood sugar levels, the glucose content in the chamber moisture and the lens increases. Water then enters the lens, causing the lens fibers to swell. Edema affects the refractive power of the lens. In 75% of patients with classical galactosemia, cataracts usually develop within the first weeks after birth. Cataract can form in any condition that leads to a decrease in the level of calcium in the blood: tetany, spasmophilia, rickets, kidney failure. In Westphal-Wilson-Konovalov's disease, copper metabolism is disturbed. With miotic dystrophy, patients have multicolor iridescent crystals in the posterior intracapsular layers of the lens. The disease is hereditary.

With a polar cataract, changes in the lens are formed in the intracapsular layers of the anterior or posterior pole of the capsule. Suture cataracts are manifested by clouding of the Y-shaped suture of the nucleus. Congenital nuclear cataract is an opacity of any embryonic nucleus. Capsular cataract is a limited clouding of the epithelium and the anterior lens capsule. Zonular cataract is a bilateral symmetrical lesion. A complete cataract is a clouding of all lens fibers. A membranous cataract occurs when the proteins of the lens are resorbed. In this case, the anterior and posterior lens capsules are soldered into a solid membrane.

Author: Shilnikov L.V.

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