A person sees through the eye, where the image is transmitted through the chiasm, the optic nerve, optic tract in special areas of the occipital lobes of the cerebral cortex. Our vision is three-dimensional due to the presence of the two eyes. The right side of the retina sends "the right side" of the image to the right side of the brain. Similarly happens with the left side of the retina. A cord connects the two parts together, getting the whole image.
In case of violation of the joint movement of the left and right eye binocular vision will be frustrated, since each eye sees only "its" picture.
- The optical function of projecting the image;
- The function of life support;
- Perception and "coding" the received information to the brain.
Eye - is a complicated optical device, whose main task is to transfer the image the optic nerve. Currently, the structure of the eye is so well studied that permit such subtle procedures like laser vision correction.
It consists of the following parts of the eye:
- Cornea - transparent shell, which is in front of the eye. The cornea does not have blood vessels, it has a large refractive power and is bordered with the sclera.
- Front camera - the space between the iris and the cornea, filled with intraocular liquid.
- Iris, which is shaped like a circle with a hole. It consists of the iris muscles that during relaxation or reduction of pupil size change. From the iris depends on the color of the eyes (if there's little pigment cells - it is blue, and if a lot - brown). The iris can be compared with the diaphragm in a camera, regulating light stream.
- Pupil - the hole in the iris. On the size of the pupil influences the light level. The more light, the smaller the size of the pupil.
- The lens - Transparent and flexible lens that can easily change its shape, almost instantaneously "focusing" on something. That is why people with good eyesight can see both from close and from a distance. The lens is located in a special capsule, which is held ciliary girdle.
- Vitreous - a transparent gel-like substance, which is located in the posterior part of the eye. Its main function is to maintain the shape of the eyeball and participation in intraocular metabolism.
- The retina, which is composed of nerve cells, and light-sensitive photoreceptors. The receptors of the retina can be divided into two types: rods and cones. They produced enzyme rhodopsin and convert light energy into electrical energy nervous tissue, that is, a chemical reaction occurs. Sticks have a high photosensitivity and allow the person to see well even in low light. Also sticks responsible for peripheral vision. Cones, on the contrary, work well only when large amounts of light. Thanks cones we can see fine details and distinguish colors.
- Sclera - the opaque outer shell of the eyeball, which is in the front part of it goes into the transparent cornea. For the six muscles attached to the sclera, through which the eye can move. Also, it is full of blood vessels and nerve endings.
- Choroid, which is located in the posterior part of the sclera. The shell is closely related to the retina and is responsible for blood supply of intraocular structures. The choroid no nerve endings, so the diseases shell person does not feel pain.
- The optic nerve, through which the image is transferred from the nerve endings in the brain.
Diseases and treatment of eye
All eye diseases can be divided into infectious and non-infectious.
Infectious diseases occur under the influence of different organisms: bacteria, viruses, fungi. It is important in these diseases eyesight test and start proper treatment of eyes, or disease can cause damage to the cornea, and even loss of vision. Infectious diseases include conjunctivitis, blepharitis and barley.
Noncommunicable diseases are the result of over-voltage, hereditary predisposition, age-related changes. The most common non-communicable diseases include dry eye syndrome, cataracts and glaucoma.
If non-communicable diseases identified in the early stages, the eye treatment has favorable projections, and therefore it is important to once every six months to pass a vision test by an ophthalmologist.
Bags and circles under the eyes
In addition to eye diseases in humans can often see the circles and bags under the eyes. Where did they come from?
The fact that the skin of the eyelids is very delicate and subtle. Due to lack of oxygen or inadequate blood supply to the blood in the capillaries of stagnant and begins to shine through. So there are dark circles under the eyes.
Their causes are many. Circles can be hereditary factors, notably the structure of subcutaneous fat, or evidence of diseases of internal organs and the endocrine system. The most common causes of under-eye circles are stress, lack of sleep and constant chronic fatigue.
Swelling and puffiness often appear as a result of the use of bedtime much alcohol, tea or coffee. The result is a stagnation of blood and lymph vessels, and as a result - the bags of the eyes in the morning.
In addition, the bags under the eyes may indicate poor kidney function, the presence of allergic reactions, inflammation of the sinuses.
Who needs a vision test?
- People with good eyesight for prevention.
- People who have vision decreases. In this case, you must complete a survey, in which the doctor may recommend wearing glasses, lenses or carry out the correction of vision.
- People who wear contact lenses. Since the lens is a foreign body, it can cause undesirable and initially subtle changes that may lead to serious consequences (e.g., ingrowth of blood vessels into the cornea). In addition, verification of the need to ensure that the doctor could see that the man can wear contact lenses, because there are contraindications to it. In this case, the doctor will advise to wear glasses or make vision correction.
- Women planning a pregnancy. Especially those women who have myopia. You will also need to undergo regular checks during pregnancy. The ophthalmologist may recommend strengthening of prophylactic conduct retinal barrier by means of laser vision correction, which will significantly reduce the risk of deterioration.
- People, after 40-50 years, as in this age group significantly increases the likelihood of ill eye diseases (glaucoma, cataracts). For treatment of the eye to be successful, it is important to detect the disease at an early stage.
- People suffering from diseases such as hypertension and diabetes.
- Children need regular eye exams, because they have the visual analyzer is in the process of development and formation, is very important and timely detect anomalies arising in the development of the child's eyes.