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 apparatus of the eye, responsible for light refraction. In this article we will talk about its structure, functions, as well as problems and diseases that may be associated with it.
Dimensions
The lens is a biconvex, elastic, and transparent formation that is attached to the ciliary body. At the same time, its rear surface adjoins the vitreous, and on the opposite side are the rear and front chambers, as well as the iris.
In an adult, the maximum thickness of the lens does not exceed five millimeters, and in diameter can reach ten. Of great importance for him is the refractive index, which is extremely heterogeneous in thickness, directly depends on the state of accommodation. This means that it directly affects the ability of the body to adapt to changes in external conditions. The human body also has the same opportunity.
At the same time, in newborns, the lens is a spherical body with the most soft consistency. During growth, its growth occurs mainly due to an increase in diameter.
Structure
In the structure of the lens there are three main elements. These are the capsular epithelium, capsule and the main substance.
A capsule is an elastic thin and structureless substance with which the lens is coated on the outside. 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 using the ciliary girdle.
Its thickness over the entire surface is heterogeneous. For example, in front it is much thicker than in 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 front and back zones. The smallest thickness in the region of the posterior pole of this organ.
Epithelium
In the structure of the lens, the epithelium is defined as a flat, single-layered and non-keratinized. Its main functions are cambial, trophic and barrier.
In this case, epithelial cells that are in accordance with the central zone of the capsule, that is, directly opposite the pupil, as close as possible to one another. Cell division in this place practically does not occur.
Moving in to the periphery from the center, one can trace a significant decrease in the size of these cells, as well as an increase in their mitotic activity. In this case, specialists observe a slight increase in cell height. All this leads to the fact that in the equatorial region the lens epithelium is already a prismatic layer of cells. On the basis of which a sprout zone is formed. It is in this place that these fibers begin to form.
The main substance of the lens
The bulk of the lens is made up of fibers. They include epithelial cells, which are thus elongated. At the same time, one fiber resembles a hexagonal prism.
The substance of the lens forms a special protein called crystallin. It is completely transparent, like the other 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; moreover, it is shortened.
An 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, as well as the participation of aqueous humor.
Percentage composition
Summing up, it can be noted that the lens consists of water for 62 percent, also it contains 35% of protein substances and about two percent of mineral salts. From this it turns out that more than a third of its total mass are proteins. In percentage terms, there are more of them than in any other organ located in the human body.
It is due to the correct ratio of proteins in the lens that one can achieve perfect transparency. However, with age, normal exchange in the eye is impaired. Which leads to the destruction of proteins and clouding of the crystalline 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 environment through which the rays of light gain unhindered access to the retina of the visual organ. This is an important function of light conduction, which is provided due to its main and unique ability to be transparent.
Another of its most important functions is light refraction. The lens in second place after the cornea in the structure of the human eye, if possible, refract the rays. This biologically living lens is capable of achieving an optical power of 19 diopters.
When interacting with the ciliary body, the third most important function of the lens, accommodation, is fulfilled, which allows it to smoothly change the optical power. Due to its elasticity, the mechanism of self-focusing of the received image becomes probable. This ensures the dynamics of refraction.
With the help of the lens, the eye is actually divided into two unequal sections. It is a large rear and a smaller front. It becomes a kind of barrier or partition between them. This barrier effectively protects the structures located in the anterior section 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 body immediately mixes forward unhindered. Anatomical changes in the relationship within the eye occur.
Lens problems
Without the lens, the conditions for ensuring the hydrodynamics of the pupil are difficult. As a result, conditions appear that can lead to the formation of secondary glaucoma.
If it is eliminated together 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, is separated 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, for example, retinal detachment, edema, rupture or hemorrhage.
The lens also serves as a natural barrier to microbes, which can penetrate directly into the vitreous body. In this, it also performs the function of a protective barrier. That's what the lens of the eye does, what significance it has for the human body.
Cataract
The main ailment that is associated with the lens of the human eye is cataract. So called full or partial opacification of the lens. Losing transparency, it no longer transmits light. Because of this, vision is greatly reduced. There is a chance that a person will go blind.
At risk due to the development of cataracts are older people. In 90 percent of cases, patients suffer from this problem due to age. In 4%, the cause is trauma; another 3% are due to congenital cataracts and newborns and radiation after radiation exposure.
It is worth noting that the development of this disease contributes to vitamin deficiency, endocrine disorders, such as diabetes mellitus, poor environmental conditions, the use of certain drugs for a long time. In recent years, more and more studies have appeared that confirm that cataracts may develop due to tobacco use.
Elderly disease
According to statistics available to the World Health Organization, about 80 percent of cases of cataracts occur after 70 years. Many consider it a disease of the elderly, although this is not a completely true statement.
Cataracts appear due to age-related changes occurring in the human body, and they each occur in due time. Therefore, in some cases, patients have to deal with cataracts not only at an advanced, but also at a working age, for example, at 45-50 years.
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, purely for the elderly human body, is a natural phenomenon, so you need to be prepared for the fact that everyone can develop cataracts.
Symptoms
With the appearance of cataracts, a person begins to see blurry, for him everything becomes blurred. This is the main symptom that allows you to know 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 impending cataracts are:
- impaired night vision;
- difficulty sewing and reading the small print;
- increased sensitivity to bright light;
- distortion and movement of objects;
- difficulty in selecting points;
- weakening of the perception of colors.
What to do?
Currently, the only effective treatment option for the lens of the eye is surgery. It is important to note that this is a complex process. It consists in removing a clouded lens. This is in this case a microsurgical operation. Which is carried out by qualified specialists. An artificial lens or, scientifically speaking, an intraocular lens, is replaced with a clouded lens. By its optical properties, this lens resembles a natural one. It has high reliability.
It should be emphasized that the changes occurring in the eye are irreversible. Therefore, special diets, glasses or exercises are not able to cure the lens, causing it to become transparent again. The widespread belief that vitamin complexes contribute to the inhibition of cataract development is not supported by any really serious scientific research.
Operation progress
Many such operations are performed annually at the Fedorov Eye Microsurgery Center. Two weeks before the operation, the patient gives blood and urine, he needs to have a chest x-ray and an electrocardiogram. Have an examination with a physician, dentist and ENT specialist. If a patient suffers from diabetes, he will need the advice of an endocrinologist.
In most cases, an operation to install an artificial lens is carried out the very next day after the patient is hospitalized in a hospital. The next morning, special drops are added to the eye, expanding the pupil, often the patient is given a sedative so that he can relax.
Cataract removal in the center "Eye Microsurgery" is carried out under a microscope. During surgery, local anesthesia is used. The patient does not fall asleep, remains conscious, for example, perceives the words of the doctor.
The surgeon makes several micro-punctures, opening the front capsule and removing the damaged lens itself. The bag in which he was located is cleared of the remnants of cellular elements. Then an artificial lens is introduced through a special system. He himself is able to deal with it as soon as he appears in the eye.
When the operation is completed, the eye is washed with a special solution. In most cases, after surgery, 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 few hours. As a rule, surgical intervention takes place without consequences.