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Cataract

 
, medical expert
Last reviewed: 01.06.2018
 
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Cataracts are congenital or acquired degenerative opacification of the lens. The main symptom is the gradual painless blurring of vision. The diagnosis is established or installed ophthalmoscopically and at inspection on slit lamp. Treatment of cataracts consists in surgical removal of the lens and implantation of the intraocular lens.

Cataract - any opacity of the lens. Recently, it has been established that with cataracts, as the turbidity progresses, the amount of common (especially soluble) protein decreases, amino acids disappear, the content of free, labile- and firmly-bound urea varies as an attendant component of the optical system. The activity of lactate dehydrohease is noticeably weakening, and a shift in the isoenzyme spectrum occurs, indicating a slowing of glycolysis rate, a decrease in tissue oxygenation, and the development of metabolic acidosis. The interrelation of the exchange processes is broken.

Thus, cataracts are a protein disease. At the basis of the development of pathological changes in the lens leading to cataracts, there are disturbances in metabolic processes. The environment, ie, environmental factors, living conditions, chronic and systemic diseases, bad habits (smoking, drinking alcohol), etc., has a significant influence on the development of these processes. Therefore, in order to prevent the progress of turbidity, it is necessary to conduct explanatory work with patients about the need to exclude smoking, regular treatment of coronary heart disease, respiratory failure, diabetes, helminthic invasion. The great importance of the day for the prevention of lens diseases is the elimination of environmentally harmful factors (radionuclides, chemicals that pollute the soil), fighting alcoholism.

The lens, unlike all other substances of the eye, grows throughout life due to the epithelium inside, into itself. This happens as follows. Lens epithelium is located in the form of a layer or millions of cells. They multiply all the time and move to the equator. When the epithelial cell reaches the equator, it becomes the mother and gives birth to lens fibers - two twins, one of which goes to the front, the other - to the posterior. The cell that gave offspring, dies, lyses. But there is no emptiness in nature, the place of this cell is occupied by her sister, and the process continues. With age, young lens fibers accumulate on the periphery, the older ones around the nucleus. The older the patient, the denser her core. Thus, the lens fibers in the process of reproduction tend to the center and collide with each other, which leads to the formation of cortical seams. The seam of the cortex is the site of the collision of the lens fibers, where a group of fibers stopped growing, that is, the rays of the lens of the star appeared-the seams of the cortex. Knowing the optical zones of the lens is necessary to accurately determine the localization of opacities and the type of cataract.

In the lens there are no vessels and nerves. In this regard, there is no inflammation in it. However, the lens work is intensive. With age, dystrophic changes appear in it, that is, there is a cataract.

Cataract - a change in the composition of the intraocular fluid in cases of penetration into it of any unusual ingredients or a lack of necessary substances in it, which leads to a disruption in the exchange in the cells of the epithelium and the fibers of the lens. For any impairment of metabolism in the cells of the epithelium, the lens fibers respond with the same reaction; they swell, grow turbid and disintegrate. The turbidity and decay of the lens fibers can also occur from mechanical damage to the lens capsule. The word "cataract" means "waterfall", which is associated with the old idea of clouding the lens as a cloudy gray film, like a waterfall descending in the eye from the top down, between the lens and the iris.

The opacity of the lens is detected by examining the eye using the method of transmitted light. In the transmitted light, partial opacities of the lens are visible as dark bands, spots on the background of the glowing red light of the pupil. Significant and complete clouding of the lens is noticeable even in side lighting. At the same time, the pupil area does not, as usual, have black color, it seems gray and even white. When studying red light in transmitted light, the pupil will not.

On examination, to see the entire lens (peripheral parts and the center), resort to medical dilatation of the pupil (instill 1% atropine, tropicamide),

In elderly people, before eye enlargement, it is necessary to measure intraocular pressure, since many drugs that dilate the pupil can increase intraocular pressure. If the patient suffers from glaucoma and needs to widen the pupil for examination, then use a 1% solution of phenamine, which slowly and moderately dilates the pupil, and after the examination the pupil is narrowed with a 1% solution of pilocarpine.

For the study of the lens, a slit lamp is most often used. Concentrated beam of light from the slit lamp, as it were, cuts the lens, gives its optical section, in which details of the normal structure and pathological changes are visible. With this method, it is possible to detect the initial changes in the lens and its capsules, while in other methods they can not yet be detected. Depending on the intensity and location of turbidity, the symptoms of clouding of the lens are visual disturbances. With small opacities of the lens, vision does not go down. A person does not notice them if they are located in the pupil area (for example, with polar cataracts).

With more significant opacity of the lens, especially its central location, the visual acuity decreases to some extent. With complete opacity of the lens, the vision is completely lost, but the ability to sense light - the light perception - remains. To make sure that when the lens is completely clouded the retina and optic nerve are functionally healthy, determine the light perception and its projection.

A patient with complete clouding of the lens can freely and correctly locate the location of the light source (lamps, candles), which indicates the preservation of the optic-nervous apparatus and its function. Opacification of the lens may affect the subject vision.

With complete opacity of the lens and a normally functioning optic-nervous apparatus, not only the light perception is retained, but also the color perception. Correct recognition of colors indicates the preservation of the function of the yellow spot.

In addition to reducing vision, patients with developing lens opacity often complain of monocular polyopia, when instead of one lamp or suppository the patient sees them in the plural. This depends on the difference in refraction in the transparent and cloudy parts of the lens.

With the beginning of cataracts, the development of myopic refraction of a weak degree in a commensurate eye is also characteristic. Elderly people who had previously seen well into the distance, and who used glasses for reading, notice that they have become worse off into the distance, and they can read without glasses. The appearance of myopia is also due to an increase in the refractive index of the turbid lens. The diagnosis of cataracts, despite the ease of detection of lens opacities, can not be done with only external examination or with side lighting, especially in the elderly, whose nucleus of the lens is compacted. Only the study in transmitted light makes the diagnosis of cataract accurate.

Opacification of the lens (cataracts) differ in their clinical picture, localization, development time and course, divided into acquired and congenital. Progressive cataracts, as a rule, are acquired, congenital - stationary.

Depending on the localization of turbidity, the following types of cataracts are distinguished: anterior and posterior polar, fusiform, zonal, nuclear, cortical, total, posterior, cup-shaped, polymorphic, coronal.

trusted-source[1], [2], [3]

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