What is myopia

Myopia is a condition of visual impairment in which a person does not see objects far from him, and can well see everything that is located nearby. Myopia is popularly called myopia.

Causes of myopia

The mechanism of operation of the organ of vision is based on the laws of physics regarding the reflection of a ray of light. When a light beam is reflected from an object and hits the eye, it encounters several optical media reflecting it again. All beams of light, wherever they fall on the organ of vision, after passing through its structure, converge on the retina. So a person gets a picture of the environment. When the angle of reflection of the light beam changes in the eye, the focus shifts from the retina. In a situation with myopia, it forms in front of the retina. Therefore, a person with myopia sees objects vaguely, but only those that are located away from him.

Causes of myopia

This is easily explained — the rays of light reflected from far-away objects fall into the organ of vision almost parallel. The same cannot be said about the rays emanating from objects nearby — the rays reflected from them have a divergent direction and after refraction in the eye converge exactly on the retina.

So that the beams of light radiating from distant objects do not come parallel to the eye, special lenses (glasses) are used, which scatter light at a certain angle. For each degree of myopia, there are lenses that change the angle of the beam in a specific way. The degree of angle change is commonly called diopters, which have a negative value. It is enough to buy glasses with the necessary “minus” to see well into the distance.

The main reason for myopia is the discrepancy between the refractive power and the optical axis of the eye. This suggests that the size of the eyeball itself is of direct importance for visual acuity. If normally a person’s eye length is from 23 to 24 mm, then for nearsighted people this value is much larger and can be 30 mm. A difference of 1 mm gives a shift in visual acuity by 1 dptr.

On the other hand, the axis may be equal to the norm, that is, with the normal length of the eyeball, myopia may also occur. The reason in this case will be changes in the strength of the optical system. That is, the rays that hit the organ of vision are refracted at too great an angle, which is why the focus shifts from the retina and is located in front of it.

In some cases, two problems merge together and give myopia. If the refraction is incorrect and the eye length is too long, myopia is inevitable. Myopia may progress, or it may remain unchanged. If myopia occurred in childhood, it may increase until the growth and development of the organ of vision is completed.

Myopia is hereditary. Studies have shown that parents who have a problem with long-distance vision, in 50% of cases, children are born with the same visual impairment. However, ophthalmologically healthy parents may also have a child with a focus disorder. Such cases have a small percentage — only 8%.

In addition to physiological disorders in the form of the size of the eyeball, the quality of vision is affected by lifestyle. Uncontrolled TV viewing, frequent visual tension associated with the bright screen of a smartphone located close to the eye, as well as insufficient illumination of the workplace inevitably leads to myopia.

Classification of myopia

Myopia is primarily divided into:

  • innate;
  • purchased.

According to the type of mechanism of education , there are:

  • axial (when the wrong size of the eyeball is to blame);
  • refractive (when the reason lies in the excessive refraction of sunlight inside the eye).

If we turn to refractometry, we can distinguish three degrees of myopia:

  • weak, which is characterized by small values of lens strength – up to -3 diopters;
  • average, it is characterized by the choice of lenses with values from -3 to -6;
  • a high degree implies the need to buy lenses with a refractive power of -6 diopters.

In ophthalmology, there are cases when the patient was ordered lenses with a refractive power of -15 and even -30 dptr.

Symptoms of myopia

At the initial stage, myopia may not manifest itself in any way. A person will not experience vision problems, and only at a professional examination by an ophthalmologist will changes in the structure of the eye be noted. The most common age for the formation and progression of myopia is school years. This is certainly due to the incorrect organization of the workplace at home, incorrect planning of classes and prolonged reading of small print.

Diagnosis of myopia

Visual disturbances should be suspected when the child begins to approach the blackboard more and more often to examine the inscription. Parents may note the appearance of squinting in a student who has not been observed before. In addition, if a child begins to complain more often of headaches in the frontal region, especially if the pain is localized in the eye sockets, one should suspect asthenopia of the muscles of the organ of vision — this is physical fatigue that the eye undergoes with myopia due to constant tension.

Diagnosis of myopia

To make a diagnosis, it is not enough to order a number in the polyclinic to an ordinary optometrist, so that, covering one eye, call letters from a template. With all the importance of this test, you can not rely only on it when monitoring the quality of vision. An ophthalmologist should use:

  • visometry using lenses of different refractive powers;
  • skiascopy to determine the refraction of the eye;
  • refractometry – to determine visual acuity;
  • conducting tests for cycloplegia — inability to focus due to paralysis of the ciliary muscle.;
  • ophthalmoscopy with a Goldman lens to determine the presence of hemorrhages, spots and dystrophy.

In some situations, the patient is offered to wear lenses (in glasses or in the form of contact lenses). In others, especially when the destruction of the lens is visible, laser treatment or surgical intervention is offered.

Leave a Reply

Your email address will not be published.