Cataract

Cataract is a congenital or acquired degenerative clouding of the lens. The main symptom is a gradual painless blurring of vision. Diagnosis is established ophthalmoscopically and by slit lamp examination. Treatment of cataract involves surgical removal of the lens and implantation of an intraocular lens.

Cataract is any clouding of the lens. It has been recently established that with cataract, as the clouding progresses, the amount of total (especially soluble) protein decreases, amino acids disappear, the content of free, labile and tightly bound urea as an accompanying component of the optical system changes. The activity of lactate dehydrogenase noticeably weakens, and a shift in the isoenzyme spectrum occurs, which indicates a slowdown in the rate of glycolysis, a decrease in tissue oxygenation, and the development of metabolic acidosis. The relationship between metabolic processes is disrupted.

Thus, cataract is a protein disease. The development of pathological changes in the lens leading to cataract is based on metabolic disorders. The development of these processes is significantly influenced by the environment, i.e. environmental factors, living conditions, chronic and systemic diseases, bad habits (smoking, alcohol consumption), etc. In this regard, in order to prevent the progression of opacities, it is necessary to conduct explanatory work with patients about the need to quit smoking, regularly treat ischemic heart disease, respiratory failure, diabetes, helminthic invasion. Of great importance in preventing lens diseases is the elimination of environmentally harmful factors (radionuclides, chemicals polluting the soil), and the fight against alcoholism.

The lens, unlike all other substances in the eye, grows throughout life due to the epithelium inside, into itself. This happens in the following way. The lens epithelium is located in the form of a layer or millions of cells. They are constantly multiplying and moving toward the equator. When an epithelial cell reaches the equator, it becomes a mother and gives birth to lens fibers - two twins, one of which goes to the anterior section, the other to the posterior. The cell that gave birth to the offspring dies, lyses. But in nature there is no emptiness, the place of this cell is taken by its sister, and the process continues. With age, young lens fibers accumulate on the periphery, older ones - around the nucleus. The older the patient, the denser the nucleus. Thus, the lens fibers in the process of reproduction tend to the center and collide with each other, which leads to the formation of cortex sutures. The cortex suture is the point of collision of lens fibers, where a group of fibers stopped growing, i.e. the rays of the lens star appeared - the cortex sutures. Knowledge of the optical zones of the lens is necessary for the precise determination of the localization of opacities and the type of cataract.

There are no vessels or nerves in the lens. Therefore, there is no inflammation in it. However, the lens works intensively. With age, dystrophic changes appear in it, i.e., cataracts occur.

Cataract is a change in the composition of the intraocular fluid in cases of penetration of any unusual ingredients or deficiency of essential substances, which leads to metabolic disturbances in the epithelial cells and lens fibers. The lens fibers respond to any metabolic disturbance in the epithelial cells with a uniform reaction: they swell, become cloudy and disintegrate. Clouding and disintegration 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 the clouding of the lens as a cloudy gray film, like a waterfall descending in the eye from top to bottom, between the lens and the iris.

Clouding of the lens is detected during an eye examination using the transmitted light method. In transmitted light, partial clouding of the lens is visible as dark stripes, spots against the background of the pupil glowing red. Significant and complete clouding of the lens is also noticeable with lateral lighting. In this case, the pupil area does not have the usual black color, it appears gray and even white. When examining in transmitted light, there will be no red glow of the pupil.

During examination, in order to see the entire lens (peripheral parts and the center), resort to medicinal dilation of the pupil (1% atropine, tropicamide are instilled),

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

A slit lamp is most often used to examine the lens. A concentrated beam of light from a slit lamp cuts the lens, giving its optical section, in which details of the normal structure and pathological changes are visible. With this method, it is possible to detect initial changes in the lens and its capsule, while with other methods they cannot yet be detected. Depending on the intensity and location of the clouding, the symptoms of clouding of the lens are visual impairment. With minor clouding of the lens, vision is not reduced. A person does not notice them if they are located in the pupil area (for example, with polar cataracts).

With more significant clouding of the lens, especially its central location, visual acuity decreases to one degree or another. With complete clouding of the lens, vision is completely lost, but the ability to sense light - light perception - is preserved. To ensure that with complete clouding of the lens the retina and optic nerve are functionally healthy, light perception and its projection are determined.

A patient with complete cataract can freely and correctly localize the location of a light source (lamp, candle), which indicates the preservation of the visual-nerve apparatus and its function. Clouding of the lens can affect object vision.

With complete opacity of the lens and a normally functioning visual-nerve apparatus, not only light perception is preserved, but also color perception. Correct color recognition indicates the preservation of the function of the macula.

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

In the case of incipient cataract, the development of a weak myopic refraction in the proportionate eye is also characteristic. Elderly people who previously had good distance vision and used glasses for reading up close, notice that they have become worse at seeing into the distance, but can read without glasses. The appearance of myopia is also caused by an increase in the refractive index of the clouding lens. The diagnosis of cataract, despite the ease of detecting lens opacities, cannot be made by external examination alone or with the help of lateral lighting, especially in elderly people whose lens nucleus is compacted. Only a study in transmitted light makes the diagnosis of cataract accurate.

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

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

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