The structure of the eye and its functions

The eye is a part of the visual analyzer that includes the optic nerve and visual centers in the cerebral cortex. The eyeball has a spherical shape, its walls lined with three membranes: the outer (or fibrous connective tissue), middle (vascular) and internal (the retina).

The fibrous sheath, it will protect the eyes from external influences, it is transparent, and the front is called the cornea. Vascular - provides power to the eyes, the front part is called the iris, the center of which there is an opening - the pupil, between the iris and choroid is the ciliary body, which carries the ciliary muscle, governing the curvature of the lens. The retina - is the nerve endings, the retina of the eye perceives the back of the image. The most clear image is obtained if the rays fall on the middle of the back of the eye, this place is called the yellow spot, next to it is the optic disc.

The inner core of the eye consists of light-refracting transparent medium (the lens, vitreous and aqueous humor), which together with the cornea of ​​the eye constitute an optical system.

Light rays entering the eye, the lens is refracted to fall on the retina of the eye and the back are transmitted by the optic nerve to the central nervous system. For a clear vision of the focus (the point where going to the lens refracted rays) must be located on the retina. This is ensured by accommodation - the ability of the lens to become more convex or less due to the reduction or relaxation of the eye muscles.

The refractive power of the eye in complete relaxation of accommodation (maximum lens flattened) is called refraction, which may be commensurate (emmetropic), farsightedness (hyperopia) or short-sighted (myopic). The amount of refraction is measured in diopters (1 diopter - is the power of a lens with a focal length of 1 m).

Myopia and its causes

Myopia - a violation of refraction of the eye in which parallel rays of light entering the eye after refractive agree not focus on the retina, but in front of it. When myopia considered the subject is clearly visible only at close range. Another name for short-sightedness - myopia Myopia - just a feature of   (squinting) is due to the fact that people see better, narrows his eyes, which contributes to a more distinct image on the retina.

Myopia occurs because the eye increases the anteroposterior direction. The axis of the eye is too high compared to its refractive power (axial myopia), or refractive system is too strong (refractive myopia).

The main cause of myopia is considered to be the weakness of the ciliary muscle, which occurs as a result of adverse conditions of visual work. The growth of the eyeball is a kind of adaptive act aimed at allowing continuous operation at a close distance from the eyes.

Signs

Myopia is divided into three levels: mild (up to 3, 0 diopters), medium (3, 0-6, 0 diopters) and high (6, 0 diopters and above). There are cases of myopia 20 0 - 30 0 diopters or even higher. The elongation axis of the eye 1 mm entails strengthening of myopia 3, 0 diopters.

Most often there are cases of mild to moderate myopia. Sometimes, nearsightedness is the so-called "flying flies", see patients in the form of small grayish haze, moving the motion of the eye.

When myopia of high to medium eyeballs few will stand forward, eye gap seems wider than normal, the pupil larger diameter.

From a high degree of myopia should be distinguished severe or progressive malignant myopia, in which there are certain changes in the membranes of the eye and the fundus.

Myopia is accompanied by an increase of the eyeball, resulting in a stretchable meninges. It is especially dangerous for a tensile choroid and retina. Blood vessels are extended, retinal breaks down food, because of which appear on its surface defects can occur even retinal detachment Retinal detachment - it is not necessary to delay the operation . Retinal detachment leads to a sharp deterioration of vision and even blindness.

Diagnosis of myopia

Initially determined by visual acuity with special lenses that correct nearsightedness.

An objective method of confirming the diagnosis of myopia is skiascopy - Monitoring of the movement of the light spot in the illuminated pupil during rotation ophthalmoscopic mirror. In normal vision, farsightedness Hyperopia - than it is fraught?   and less than 1 diopter myopia light spot moves in one direction, while myopia above 1, 0 diopters - in another.

Work is also refractometry eye - measurement of refraction with the help of special equipment - refractometer.

For inspection of the fundus (the visible inner surface of the eyeball) is performed ophthalmoscopy - examination by an increase in a certain area of ​​the inner surface of the eyeball by using an ophthalmoscope.

Using ultrasound can measure the length of the eyeball, and the thickness of the cornea at different sites.

Treatment

Most cases require only correction of myopia glasses. Progressive malignant myopia requires a systematic general and local treatment.

At high myopia and a significant decrease in visual acuity normal glasses often do not provide adequate improvement of view, in such cases appoint telescopic glasses, which have the appearance of small binoculars. With contact lenses Contact lenses - whether they can completely replace the glasses? It is worn on the front surface of the eyeball, perhaps more than with eyeglasses, vision improvement, especially in the high myopia.

In recent years, increasingly myopia treated surgically. Using a special laser removes a thin layer of the cornea, reducing its refractive power and eliminate nearsightedness. With a high degree of myopia lens is removed and in its place put a soft lens which has the necessary refractive properties.

  Galina Romanenko

Cataract surgery: the preparation and operation

Before the surgery, the doctor will discuss with you exactly how it will go, and will ask you a number of questions regarding the medicines you are taking, and the previously transferred diseases. He may ask you to stop taking certain medicines a few days before the operation. In addition, the survey is conducted, the results of which the doctor can decide what you need intraocular lenses.

In the room where the operation is conducted, will be a few people - an anesthesiologist, surgeon and assistants. Before the operation the anesthesiologist usually tells the patient what medications he will use, and how they act. Although cataract surgery is usually not too painful, painkillers still used to reduce discomfort to a minimum. Directly cataract removal takes about twenty minutes. During the procedure, the patient may feel the pressure of various tools used by the surgeon, but not pain.

When the operation is completed, the patient is transferred to the ward where he can stay for a couple of hours. The doctor will prescribe to the patient several types of droplets which it should be used after surgery. Most people go home the same day. Many people after cataract feel some discomfort - this is normal; However, the sudden loss of vision or severe pain should seek medical attention immediately.

The postoperative period in cataract extraction

The patient should be examined in a few days and weeks after surgery .  Typically, rehabilitation after cataract surgery is quick and without complications .  After a few days in most patients vision improved so that they can return to work .  Recommendations after cataract surgery is usually to eye drops for a few weeks - this is necessary to prevent infections and inflammations .  Observe special restrictions after cataract surgery is not required, although many patients within a few days is not advisable to drive a car, and for some time on a clear day you need to wear sunglasses .  Exactly how much lasts rehabilitation after cataract depends on what type of operation has been used for its removal, as well as on the overall health of the patient .  Points discharged after cataract surgery when vision is completely stabilized .

Complications of cataract surgery

Although approximately 98% of cataract operations are successfully and without adverse health effects, patients sometimes develop certain complications .  Before the surgery, the doctor explains to the patient what is the likelihood of complications is in it - it depends on the presence of comorbidities, type of operation, and other factors .  The most common complication following cataract surgery - a persistent inflammation, changes in intraocular pressure, infection and retinal detachment .  If the capsule of the lens was damaged during surgery, it may require additional surgery to place the artificial lens to another location .  In some cases, the IOL is displaced or not functioning properly because of which need further surgery to move it, replace, or delete .  These complications are rare, but they may lead to significant vision loss, so after surgery patients should be screened regularly .

Sometimes after a few months or years after surgery thin capsule of the lens becomes cloudy, which is why the vision begins to deteriorate. The patient may seem that he has re-developed cataract surgery - a violation called PCO lens or secondary cataract Secondary cataracts - a common postoperative complication . In such cases, it may require treatment of cataract laser. This procedure takes only a few minutes, and after the vision usually improves quickly.

Cataract surgery in diabetes

Before the surgery, diabetics are the same survey, the rest of the patients, with the difference that doctors pay special attention to various changes in the structure of the eye caused by diabetes. In diabetic cataract Cataracts - how to solve the problem completely?   It develops at an earlier age than it does on average, and they have increased the likelihood of developing secondary cataract surgery. In diabetes Diabetes - threatening and incurable disease   may be designated cataract laser - is less invasive than other procedures for the treatment of cataract, which is particularly important in case the patient has an ocular disease associated.

Laser surgery for cataract minimizes the risk of damage to the lens capsule and other complications. After this operation can also be implanted IOL. Unfortunately, laser treatment of cataract are not always sufficiently effective, and sometimes removal of the lens in diabetics using other procedures. It is important that after the operation, patients are not only regularly used the eye drops, which they wrote the doctor, but also carefully monitor your blood sugar Blood sugar - one of the main indicators of human health   - It helps to speed up the recovery process. Even if the operation was carried out flawlessly in the postoperative period may aggravate the symptoms of diabetic retinopathy so patients should be sure to regularly examined by a specialist.