The lens is a transparent body that is located inside the eyeball directly opposite the pupil. In fact, it is a biological lens, constituting an important part of the eye apparatus responsible for light refraction. In this article, we will talk about its structure, functions, as well as the problems and diseases that may be associated with it.
Sizes
The lens is a biconvex, elastic and transparent formation that is attached to the ciliary body. At the same time, its posterior surface is adjacent to the vitreous body, and on the opposite side are the posterior and anterior chambers, as well as the iris.
In an adult, the maximum thickness of the lens does not exceed five millimeters, and in diameter it can reach ten. Of great importance for him is the refractive index, which is extremely inhomogeneous in its thickness, directly depends on the state of accommodation. This means that it is directly influenced by the ability of the organadapt to changing external conditions. The human body has the same ability.
At the same time, in newborns, the lens is a spherical body with the softest consistency possible. During maturation, its growth occurs mainly due to an increase in diameter.
Building
There are three main elements in the structure of the lens. These are the capsular epithelium, capsule and ground substance.
A capsule is an elastic, thin and structureless substance that covers the outside of the lens. It looks like a transparent shell of a homogeneous type, which has the ability to strongly refract light, protecting the lens itself from the effects of pathological and harmful factors. In this case, the capsule is attached to the ciliary body with the help of a ciliary band.
Its thickness over the entire surface is not uniform. For example, the front is much thicker than the back. This is explained by the fact that on the front surface there is only one layer of epithelial cells. It reaches its maximum thickness in the anterior and posterior zones. The smallest thickness is in the region of the posterior pole of this organ.
Epithelium
In the structure of the lens, the epithelium is defined as flat, single-layered and non-keratinizing. Its main functions are cambial, trophic and barrier.
In this case, epithelial cells that are in line with the central zone of the capsule, that is, directly opposite the pupil, as close as possible to one another. Division into cells in this place practically does not occur.
Moving to the periphery from the center, one can trace a significant reduction in the size of these cells, as well as an increase in their mitotic activity. At the same time, experts observed a slight increase in the height of the cells. All this leads to the fact that in the region of the equator the lens epithelium is already a prismatic layer of cells. On the basis of which the growth zone is formed. This is where these fibers begin to form.
The main substance of the lens
The bulk of the lens is fibers. They include epithelial cells, which are maximally elongated. One fiber resembles a hexagonal prism.
The substance of the lens forms a special protein called crystallin. It is completely transparent, like the rest of the components that make up the light-refracting apparatus. This substance is devoid of nerves and blood vessels. The denser part of the lens, located in the center, does not have a nucleus, and besides, it is shortened.
The important point is that during the development of a person in the womb, the lens receives the nutrition it needs directly through the vitreous artery. Then everything happens differently. When a person grows up, the basis of nutrition is the interaction of the lens and the vitreous body, as well as the participation of aqueous humor.
Percentage composition
Summing up, it can be noted that the lens is 62 percent water, it also contains 35% proteins and about two percent mineral s alts. From thisit turns out that more than a third of its total mass is proteins. In percentage terms, there are more of them than in any other organ in the human body.
It is precisely due to the correct ratio of proteins in the lens that it is possible to achieve perfect transparency. However, with age, normal metabolism in the eye is disrupted. Which leads to the destruction of proteins and clouding of the transparent substance of the lens. We will dwell on this problem in more detail.
Functions
A number of functions of the lens of the eye make it very important for the human body. First of all, it becomes a kind of medium through which light rays get unhindered access to the retina of the visual organ. This is an important function of light transmission, which is ensured by its main and unique ability to be transparent.
Another of its most important functions is light refraction. The lens is in second place after the cornea in the structure of the human eye, as far as possible to refract rays. This biologically living lens is capable of reaching a power of 19 diopters.
When interacting with the ciliary body, the third most important function of the lens, accommodation, is performed, which allows it to change its optical power as smoothly as possible. Due to its elasticity, a mechanism for self-focusing of the received image becomes possible. This ensures dynamic refraction.
With the help of the lens, the eye is actually divided into two unequal sections. This is a large rear and a smaller front. He becomesa kind of barrier or partition between them. This barrier effectively protects structures located in the anterior region when they are under strong vitreous pressure. If for some reason the eye is left without a lens, this is fraught with sad consequences, since the vitreous immediately moves forward without hindrance. There are anatomical changes in the relationship within the eye.
Problems of missing lens
Without a lens, the conditions for ensuring the hydrodynamics of the pupil are difficult. The result is conditions that can lead to secondary glaucoma.
If it is eliminated along with the capsule, significant transformations occur in the posterior region due to the resulting vacuum effect. The fact is that the vitreous body receives some freedom of movement, separates from the posterior pole, starting to hit the walls of the eye with each movement of the eyeball. This is the cause of various pathologies, such as retinal detachment, retinal edema, rupture or hemorrhage.
Also, the lens serves as a natural barrier to microbes that can penetrate directly into the vitreous body. In this, it also performs the function of a protective barrier. This is what the lens of the eye does and what it means to the human body.
Cataract
The main ailment associated with the lens of the human eye is cataract. So called complete or partial clouding of the lens. losingtransparency, it no longer transmits light. Vision is greatly reduced as a result. There is a possibility that the person will go blind.
The elderly are at risk due to the development of cataracts. In 90 percent of cases, patients suffer from this problem due to age. In 4%, the cause is trauma, another 3% are congenital cataracts and newborns and radiation after radiation exposure.
It is worth noting that the development of this disease contributes to beriberi, endocrine disorders, such as diabetes, poor environmental conditions, taking certain medications for a long time. In recent years, there has been a growing body of research confirming that cataracts can develop due to tobacco use.
Disease of the elderly
According to statistics available to the World He alth Organization, approximately 80 percent of cataracts occur after age 70. Many consider it a disease of the elderly, although this is not entirely true.
Cataract appears due to age-related changes that occur in the human body, and they all come at the right time. Therefore, in some cases, patients have to deal with cataracts not only in old age, but also in working age, for example, at 45-50 years old.
The main cause of the disease is a radical change in the biochemical composition of the lens. It occurs as a result of age-related processes in the body. A cloudy lens, especially for an elderly human body, is a natural phenomenon, so you need to be prepared for the fact thatAnyone can develop a cataract.
Symptoms
When a cataract appears, a person begins to see fuzzy, everything becomes blurry for him. This is the main symptom that allows you to recognize the disease. It indicates that the clouding has already touched the central zone of the lens. In this case, surgical treatment is required.
Early symptoms of an impending cataract are:
- deterioration of night vision;
- difficulty sewing and reading fine print;
- heightened sensitivity to bright light;
- distortion and movement of objects;
- difficulty in scoring process;
- weakening the perception of colors.
What to do?
Currently, the only effective treatment for the lens of the eye is surgery. It is important to note that this is a complex process. It consists in removing the clouded lens. In this case, we are talking about a microsurgical operation. Conducted by qualified professionals. An artificial lens or, scientifically speaking, an intraocular lens, replaces a clouded one. In terms of its optical properties, this lens resembles a natural one. It is highly reliable.
It should be emphasized that the changes that occur in the eye are irreversible. Therefore, special diets, glasses or exercises are not able to cure the lens by causing it to become transparent again. The widespread opinion that the inhibition of the development of cataracts is facilitated byvitamin complexes, not backed by any really serious scientific research.
Progress of operation
Yearly, many such operations are performed at the Fedorov Eye Microsurgery Center. Two weeks before the operation, the patient donates blood and urine, he needs to do a chest x-ray and an electrocardiogram. Get examined by a therapist, dentist and otorhinolaryngologist. If the patient suffers from diabetes, he will need the advice of an endocrinologist.
In most cases, the operation to install an artificial lens is carried out the very next day after the patient's admission to the hospital. In the morning, special drops are instilled into the eye, dilating the pupil, often the patient is given a sedative so that he can relax.
Cataract removal at the Fedorov Eye Microsurgery Center is performed under a microscope. Local anesthesia is used during surgery. The patient does not fall asleep, remains conscious, for example, perceives the doctor's words.
The surgeon makes several micro-punctures, opening the anterior capsule and removing the damaged lens itself. The bag in which he was, is cleared of the remnants of cellular elements. Then, through a special system, an artificial lens is introduced. He is able to deal with himself as soon as he gets into the eye.
When the operation is completed, the eye is washed with a special solution. In most cases, after the operation, the patient remains in the hospital for one to two days. If the operation was performed on an outpatient basis, then the patient is sent home after a fewhours. As a rule, surgical intervention passes without consequences.
