Myopia


Myopia

Description myopia

Myopia is a disease that currently affects about one third of the population. It is the most common disorder of the group refractive errors of the eye, which are far more affected than urban residents villagers.

Depending on the number of diopters myopia is divided into 3 stádia- first is light myopia (myopia simplex into -3D), followed by Central nearsightedness (myopia Modica, -3 to -6 D), and the highest degree of myopia is severe myopia (myopia gravis, over – 6D). While the first two forms represent a variant of normal development (also called myopia Physiologica), the third may already be associated with severe eye.

Light and medium myopia typically occur at school age, most are exacerbated in puberty and after completion of the growth of its development stops. The severe form of myopia, but manifests in early childhood, during adolescence may decrease by up to 4 diopters per year and can lead to other, degenerative eye damage.

Risk factors for myopia

The human eye is an optical system whose refracting ability accounts for most of the cornea and lens. Refraction means bending the light beam at the interface of two media. It is expressed as the ratio between the anteroposterior length of the eye and its refractive optical power systems.

For normal vision is important because the spherical shape of the eye, and also proper curvature of the cornea and lens. It is placed inside the eye on the front part and the change of its shape, allows the eye accommodate, thus change its refractive optical power system and thus display objects located at any distance from the eye, sharply.

In a healthy eye, the entering light beams at interfaces of optical media break and fall exactly on the retina, to the point of sharpest vidění- yellow spots. Healthy eye to see well and does not need any vision correction.

Consequently an enlarged anterior-posterior length of the eye, there is a converging beam before the retina and the retina is then formed blurred image. Extension of this axis of the eye is the most common cause of myopia, which is then called axial, or axial myopia. Another cause of myopia is arefractive (index) myopia, which is increased by the curvature of the cornea or lens.

The causes of this disease are not well understood. It is a summary of inherited conditions and various external factors, which have resulted in changes in the growth of the eye. The cause may be an abnormal shape of the orbit in which the eye is saved or failures in the structure of the eyeball (the inferiority of its walls causing the failure to maintain its normal shape).

It is important however to note that part of the work, requiring a long, focusing on fine detail sight close to the eye, and especially in poor lighting, can also contribute to the development of myopia.

prevention of myopia

Myopia is a disease whose incidence has been rising in the world.

In the context of genetic predisposition for it is not recommended marriage partners who both have severe myopia. Of course, important is a varied diet in children, especially during times of increased growth. It is necessary and appropriate lighting and maintaining the proper distance in activities that strain the eye to prevent eyestrain.
It is also important to ensure the right career choice for young people with a predisposition to myopia. It is recommended to those in which there are no requirements on visual acuity, and that could possibly be performed even with poor eyesight.

symptoms of myopia

The main symptom of the disease is blurred, blurred distance vision that the patient is looking into the distance trying to improve mhouřením eyes, because through narrowed eyes slit gaining a better picture (from this symptom also comes onemocnění- myopia name in Greek means “eyes closed”).

treatment of myopia

Myopia can not be cured, there are no medications that the patient’s condition could improve. The only treatment for the disease involves prescribing a suitable correction of visual defects.

Ophthalmologist investigates visual acuity (VA). The starting point for determining the visual acuity is to determine a so-called minimum angle of resolution, which is the angle at which the eye is able to perceive two separated points as two.

To determine the visual acuity use two types of examination. The main method comprises investigative subjective tests, in which the visual acuity tested separately for each eye and then for both eyes at once. The subjective is called because it requires the active cooperation of the patient.

The patient stands at a distance of 6 meters from the board called test type that hangs on the wall, and from that reads the letters or numbers (for children using pictures). The characters are written in several rows, and in each subsequent line are smaller than the previous. Size of the characters in each row are precisely calculated so that the base (smallest) sign is seen in the healthy eye from a distance of 6 meters from the perspective of five minutes, and its details from the perspective of one minute. All other characters are then multiples of those values, it means that the visual angle of five minutes it is possible to distinguish them from a distance of 12, 24, 60 meters. The value of visual acuity is called fractional, the numerator shows the distance from the patient optotype (6 meters), and the denominator size of the smallest feature that patient still able to read without difficulty. Normal vision refers fraction 6/6, with the myopia that fraction decreases (eg 6/24).Vision is first investigated without correction, and then tested lenses of various diopters to select the optimum correction.

As an objective examination of the examination indicates automatic refractometer, which projects an image on the retina and automatically analyzes necessary number of diopters, necessary to correct the defects.

Myopia is corrected by diffusing (concave, minus) lenses, which adjust the angle of the rays incident to the eye, so that the image is formed to the retina, and not before it.

The patient has several options, how will their eye defect corrected. The first option representglasses. There is currently a wide range of spectacle frames, with a choice that will gladly help optician. Spectacle lenses can also be improved, whether a UV filter, anti-reflective layer at high diopters also can make special high refraction glass, which reduces the thickness of the lens up to 60%. There are also no dark glasses diopter that provide comfort even in very sunny weather.

Someone better suited to contact lenses, which are now available in almost all diopters, the offer is also extended to include colored lenses, which can only highlight, or even completely obscuring the original eye color. They are especially popular among young people who love to experiment with his appearance.

At present, we extend the range of laser eye surgery that gets rid of the patients refractive disorders altogether. Their essence is the removal of a few thousandths of a millimeter thick slices the cornea and thus correct the surface so as to act as a diffusion lens.

Surgery eye surgery is used in more severe refractive errors of the eye, or damaged lens patient.They consist in replacing the lens of the eye, or the insertion of additional, accessory lenses to existing and subsequent treatment of refraction of incoming rays.

The method myopia solution depends on the patient’s condition, complications of the disease, any other ocular and other diseases, and not least from its budget. The patient would have in deciding to follow the recommendations of his ophthalmologist, who has a different kind of solution refractive errors experience and is able to estimate their effectiveness in the individual patient.

How can I help myself?

For existing myopia are only effective prevention against further deterioration of eyesight regular checkups with an ophthalmologist.

Especially in children and adolescents it is necessary to guard wearing glasses, so it is important to get the kids chose, where possible, also glasses that they will love and who will love to wear.

complications of myopia

At very high levels of myopia (diopter below -15 to -20) is due to the inferiority of ligament eyeball strong stretching the rear wall. This causes degenerative changes in the choroid, retina and vitreous (gel body fills the eyeball), which could result in loss of vision in the central part zorního field, or the emergence of disturbing shadows that overlap patients seen picture.

Severe myopia is sometimes associated with glaucoma.

Other names: myopia, myopia simplex, Modica myopia, myopia gravis, light myopia, mild nearsightedness, severe myopia, congenital myopia

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