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 sheath is the cornea and sclera. Through the cornea, the refracted light rays enter the organ of vision. The opaque sclera acts as a framework and has protective functions.
Through the choroid, the eyes are nourished by blood, which contains nutrients and oxygen.
Under the cornea is the iris, which provides color to the human eye. In the center of it is a pupil that can change size depending on the lighting. Between the cornea and the iris is intraocular fluid that protects the cornea from germs.
The next part of the choroid is called the ciliary body, due to which the intraocular fluid is produced. The choroid is in direct contact with the retina and provides it with energy.
The retina consists of several layers of nerve cells. Thanks to this organ, the perception of light and the formation of an image are ensured. After that, 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 transparent intraocular fluid, the lens and the vitreous body. The vitreous has a jelly-like appearance.
An important component of the human visual system is the lens. The function of the lens is to ensure the dynamism of the eye optics. 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 it in this article.
Building
This organ is similar to a biconvex lens, the front and back surfaces of which have different curvatures. The central part of each of them is the poles, which are connected by an axis. The axis length is approximately 3.5-4.5 mm. Both surfaces are connected along a contour called the equator. An adult has an optical lens size of 9-10 mm, a transparent capsule (anterior bag) covers it on top, inside which there is a layer of epithelium. The posterior 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. Nerve endings, blood vessels, lymphoid tissue are absent from the lens, this is entirelyepithelial 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.
The composition of the lens
The composition of this organ 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.
Working principle
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 operation of the lens is to focus the rays of light reflected from the object into the macular zone of the retina. In order for the image on the retina to be clear, it must be transparent. When light hits the retina, an electrical impulse occurs, which travels through the optic nerve to the visual center of the brain. The job of the brain is to interpret what the eyes see.
Functions of the lens
The role of the lens in the functioning of the human vision system is very important. First of all, it has a light-conducting function, that is, it ensures the passage of the light flux to the retina. The light-conducting functions of the lens are provided 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 accommodative mechanism is ensured, with the help of which the focusing of the visible image is spontaneously adjusted.
This organ helps us to easily shift our gazefrom distant objects to those that are close, which is provided by a change in the refractive power of the eyeball. With the contraction of the fibers of the muscle that surrounds the lens, there is a decrease in the tension of the capsule and a change in the shape of this optical lens of the eye. It becomes more convex, due to which nearby objects are clearly visible. When the muscle relaxes, the lens flattens out, allowing you to see distant objects.
In addition, the lens is a partition that divides the eye into two sections, thereby protecting 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. This manifests the protective functions of the lens.
Diseases
The causes of diseases of the optical lens of the eye can be very diverse. These are violations of its formation and development, and changes 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 a pathology such as cataracts, or clouding of the lens. Depending on the location of the turbidity zone, there are anterior, layered, nuclear, posterior and other forms of the disease. Cataracts can be either congenital or acquired during life as a result of trauma, age-related changes, and a number of other reasons.
Sometimes injuries and breakage of the threads that provide the correctposition 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 subluxation.
Symptoms of lens damage
With age, the visual acuity of a person decreases, it becomes much more difficult to read at close range. The slowdown in metabolism leads to changes in the optical properties of the lens, which becomes denser and less transparent. The human eye begins to see objects with less contrast, the image often loses color. When more pronounced opacities develop, visual acuity is significantly reduced, cataracts occur. The location of the opacity affects the degree and speed of vision loss.
Age-related turbidity develops for a long time, up to several years. Because of this, impaired vision in one eye can go unnoticed for a long time. But even at home, you can determine the presence of cataracts. To do this, you need to look at a blank sheet of paper with one, then with the other eye. In the presence of the disease, it will seem that the leaf is dull and has a yellowish tint. People with this pathology need bright lighting in which they can see clearly.
Cloudy lens can be caused by an inflammatory process (iridocyclitis) or long-term use of drugs that contain steroid hormones. Various studies have confirmed that clouding of the optical lens of the eye occurs faster in glaucoma.
Diagnosis
Diagnosis consists of visual acuity testing andstudy of 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 that lead to a decrease in visual acuity. When examining the lens, the method of lateral focal illumination is used, in which its front surface, located within the pupil, is examined. If there are no opacities, the lens is not visible. In addition, there are other research methods - examination in transmitted light, examination with a slit lamp (biomicroscopy).
How to treat?
Treatment is mostly 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. Surgery is the only procedure that ensures complete recovery. Extracapsular extraction with suturing of the cornea can be used to remove cataracts. There is another method - phacoemulsification with minimal self-sealing incisions. The removal method is chosen depending on the density of opacities and on the state of the ligamentous apparatus. Equally important is the experience of the doctor.
Since the eye lens plays an important role in the operation of the human vision system, various injuries and violations of its work often lead to irreparable consequences. The slightest sign of visual impairment or discomfort in the eye area is a reason to immediately contact a doctor whowill diagnose and prescribe the necessary treatment.
