The human eye is a complex optical system whose task is to transmit the correct image to the optic nerve. The components of the organ of vision are fibrous, vascular, retinal membranes and internal structures.
The fibrous membrane is the cornea and sclera. Refracted light rays enter the organ of vision through the cornea. An opaque sclera plays the role of a frame and has protective functions.
Through the choroid, the eyes are fed with blood, which contains nutrients and oxygen.
Under the cornea is the iris, which provides the color of the human eye. In the center of it is a pupil that can change size depending on lighting. Between the cornea and the iris, there is an intraocular fluid that protects the cornea from germs.
The next part of the choroid is called the ciliary body, due to which the production of intraocular fluid occurs. The vascular membrane is in direct contact with the retina and provides it with energy.
The retina is made up of several layers of nerve cells. Thanks to this organ, the perception of light and image formation are provided. After this, information is transmitted through the optic nerve to the brain.
The inner part of the organ of vision consists of the anterior and posterior chambers filled with clear intraocular fluid, the lens and the vitreous. The vitreous has a jelly-like appearance.
An important component of the human visual system is the lens. The lens functions - ensuring the dynamics of the optics of the eye. It helps to see different objects equally well. Already at the 4th week of embryo development, the lens begins to form. The structure and functions, as well as the principle of operation and possible diseases, we will consider in this article.
Structure
This organ is similar to a biconvex lens, the front and rear surfaces of which have different curvatures. The central part of each of them is the poles, which are connected by an axis. The length of the axis is approximately 3.5-4.5 mm. Both surfaces are connected along a circuit called the equator. An adult has the size of an optical lens of the eye 9-10 mm, on top of it is covered by a transparent capsule (front bag), inside which is a layer of epithelium. The back capsule is located on the opposite side, it does not have such a layer.
The possibility of growth of the eye lens is provided by epithelial cells, which are constantly multiplying. The nerve endings, blood vessels, lymphoid tissue in the lens are absent, this is a completely epithelial formation. The transparency of this organ is affected by the chemical composition of the intraocular fluid, if this composition changes, clouding of the lens is possible.
Lens composition
The composition of this body is as follows - 65% water, 30% protein, 5% lipids, vitamins, various inorganic substances and their compounds, as well as enzymes. The main protein is crystallin.
Principle of operation
The lens of the eye is the anatomical structure of the anterior segment of the eye, normally it should be perfectly transparent. The principle of the lens is to focus light rays reflected from the object into the macular region of the retina. For the image on the retina to be clear, it must be transparent. When light enters the retina, an electrical impulse arises that passes through the optic nerve into the visual center of the brain. The brain's task is to interpret what the eyes see.
Lens functions
The role of the lens in the functioning of the human vision system is very important. First of all, it has a light guide function, that is, it ensures the passage of the light flux to the retina. The photoconductive functions of the lens are ensured by its transparency.
In addition, this organ takes an active part in the refraction of the light flux and has an optical power of about 19 diopters. Thanks to the lens, the functioning of the accommodation mechanism is ensured, with the help of which the focus of the visible picture is spontaneously adjusted.
This organ helps us easily glance from distant objects to those that are nearby, which is provided by a change in the refractive power of the eyeball. When the fibers of the muscle that surrounds the lens are contracted, the tension of the capsule decreases and the shape of this optical lens of the eye changes. It becomes more convex, due to which objects located near are clearly visible. When the muscle relaxes, the lens becomes flat, this allows you to see objects located far away.
In addition, the lens is a septum that divides the eye into two sections, which ensures protection of the anterior sections of the eyeball from excessive pressure of the vitreous body. It is also an obstacle to microorganisms that do not enter the vitreous body. In this, the protective functions of the lens are manifested.
Disease
The causes of diseases of the optical lens of the eye can be very diverse. This is a violation of its formation and development, and a change in location and color that occur with age or as a result of injuries. There is also an abnormal development of the lens, which affects its shape and color.
Often there is such a pathology as cataract, or clouding of the lens. Depending on the location of the turbidity zone, there is anterior, layered, nuclear, posterior and other forms of the disease. Cataracts can be either congenital or acquired throughout life as a result of injuries, age-related changes, and a number of other reasons.
Sometimes injuries and rupture of the threads, which ensure the correct position of the lens, can lead to its displacement. With a complete rupture of the threads, a dislocation of the lens occurs, a partial rupture leads to a subluxation.
Symptoms of the lens
With age, the visual acuity of a person decreases, it becomes much harder to read from close range. Slowing metabolism leads to changes in the optical properties of the lens, which becomes more dense and less transparent. The human eye begins to see objects less contrasting, the image often loses color. When more pronounced opacities develop, visual acuity is significantly reduced, and cataracts occur. The location of turbidity affects the degree and speed of vision loss.
Age-related clouding develops for a long time, up to several years. Because of this, impaired vision in one eye may go unnoticed for a long time. But even at home, you can determine the presence of cataracts. To do this, look at a blank sheet of paper with one, then the other eye. If there is a disease, it will appear that the leaf is dull and has a yellowish tint. People with this pathology need bright lighting in which they can see well.
The clouding of the lens can be caused by the presence of an inflammatory process (iridocyclitis) or prolonged use of drugs that contain steroid hormones. Various studies have confirmed that with glaucoma, clouding of the optical lens of the eye is faster.
Diagnostics
Diagnosis consists of checking visual acuity and studying the structure of the eye with a special optical device. The ophthalmologist evaluates the size and structure of the lens, determines the degree of its transparency, the presence and localization of opacities, which lead to a decrease in visual acuity. When examining the lens, the method of lateral focal illumination is used, in which its front surface, which is located within the pupil, is examined. If there is no clouding, the lens is not visible. In addition, there are other methods of research - examination in transmitted light, research using a slit lamp (biomicroscopy).
How to treat?
The treatment is mainly surgical. Pharmacy chains offer various drops, but they are not able to restore the transparency of the lens, and also do not guarantee the cessation of the development of the disease. The operation is the only procedure that ensures complete recovery. Extracapsular extraction with suturing on the cornea can be used to remove cataracts. There is another method - phacoemulsification with minimal self-sealing sections. The removal method is chosen depending on the density of turbidity and on the state of the ligamentous apparatus. No less important is the experience of the doctor.
Since the eye lens plays an important role in the process of the human vision system, various injuries and violations of its work often lead to irreparable consequences. The slightest signs of visual impairment or discomfort in the eye area are a reason for immediately contacting a doctor who will diagnose and prescribe the necessary treatment.