myopia
Synonyms in a broader sense
Medical: myopia
Astigmatism, farsightedness
English: Myopia, nearsightedness (American), shortshightedness, purblindness
Definition of myopia
Nearsightedness (myopia) is a type of ametropia in which the relationship between the refractive power and the length of the eyeball is incorrect. Strictly speaking, the eyeball is too long (axial myopia) or the refractive power is too strong (refractive myopia). The focal point of parallel incident rays is thus in front the retina. The short-sighted person can see objects in the vicinity well, but objects further away are only perceived as blurred or blurred.
root cause
- Axial myopia (axillary nearsightedness) is more common than refractive myopia (refractive nearsightedness), is partly inherited and is mostly congenital.
It occurs significantly more frequently in premature babies than in full term babies. This type of myopia develops especially in the first 30 years of life due to excessive elongation of the eyeball.
Often one hears reading in poor light or extreme close work can lead to myopia. These factors are discussed but are controversial. However, new findings indicate that poor vision (not to be confused with seeing in poor light!), E.g. an existing myopia that could promote this. - The rather rare refractive myopia (refractive nearsightedness) is caused by an increased refractive power of the cornea or lens. The cause of an increased refractive power of the lens can e.g. a clouding caused by a cataract (cataract).
Disease development of myopia
In order for a point to be seen clearly, it must be mapped exactly on the retina. This means that the focal point of parallel incident rays must fall exactly on the retina.
In people with myopia, the focus is generally after front postponed.
Either because the longitudinal diameter of the eye is too large (often) or the refractive power of the optical apparatus is too strong (rarely). As a result, objects that are far away cannot be shown in focus. Objects lying closer, however, do.
Even points that are so close to the eye that a normal sighted person can no longer focus on them can be affected by myopic (myopic) People can still be seen well.
To understand why a person is nearsighted, one has to know how the eye can sharpen objects at close and high distances. This is done with the help of the so-called optical apparatus (cornea and lens).
The lens is elastically shaped and hung behind the iris via a holding device. With the help of a sphincter muscle (ciliary muscle), the focus can be set on objects that are close or distant. As the muscle tenses, the ligaments from which the lens is hung slack and the lens sags a little. This results in an increase in the refractive power and the focal length becomes smaller, i.e. the focal point is shifted forwards. In this way, objects that are relatively close to the eye can be brought into focus. When focusing on distant objects, the ciliary muscle relaxes and the refractive power decreases, or the focal point is shifted further back.
The strength of myopia is expressed in diopters (dpt). That is the reciprocal of the focal length. The values always refer to the far point, i.e. the point at which the eye can see without accommodation (Change the focus of your view of distant or nearby objects) is a bit sharp. This lies with the person with normal vision (Emmetropes) at infinity. A nearsighted person with a myopia of -2.0 D has his far point at a distance of 50 cm. Objects that are further away from the eye can only be perceived blurred.
In contrast to farsightedness, a person with nearsightedness cannot compensate for his nearsightedness with the help of accommodation, since the ciliary muscle, i.e. the muscle that is responsible for focusing, cannot be relaxed further than it already is.
Myopia try to reduce the circles of confusion on the retina by blinking. This improves the image sharpness (stenopean vision).
Read more on the topic: Improve myopia
Risk of retinal detachment
Due to the mostly elongated eyeball, nearsightedness - in contrast to farsightedness - has an increased risk of detachment of the retina (retina). The reason is the increased tension in the retina due to the elongated eyeball, which can lead to retinal detachment. In some cases, the elongated eyeball can also lead to a detachment of the vitreous humor.
Forms of myopia
There are two types of myopia:
- Myopia simplex
- Myopia maligna.
Myopia simplex begins around the age of 10 and comes to a standstill at around 20 years of age.
Myopia maligna is constantly progressing.
Symptoms / complaints
Signs of illness (symptoms) are primarily problems with seeing in the distance, especially at night.
Sometimes an inward squint (convergent strabismus) can also indicate nearsightedness. A possible liquefaction of the vitreous body (due to the rapid growth in length of the eyeball) can also lead to the patient apparently noticing so-called "floating flies" (floaters).
This can be classified as harmless at first, but should be clarified by an ophthalmologist (specialist in ophthalmology) due to the increased risk of retinal detachment.
Read more on the topic: Eye pain
Here go to the main article: Blurred vision - what's behind it?
Diagnosis of astigmatism
Either the ophthalmologist or the optician can use the refractive power determination (Refraction determination), so of a kind Eye test determine if it is a Nearsightedness (myopia) acts.
Excursus: go to an ophthalmologist or an optician?
Many patients who have problems with the Visual acuity are wondering whether to go to the ophthalmologist or the optician. The ophthalmologist is seen as a real specialist in eye diseases and the optician as a specialist in glasses and contact lenses. Therefore the question is not that easy to answer.
In general, it can be said that both the ophthalmologist and the optician can identify the problem of visual acuity. This does not mean that one can do better than the other. It depends a lot more on the experience of the individual. So as long as you know for sure, the problem with visual acuity is really just a solitary one Farsightedness, myopia or Astigmatism / astigmatism, it does not matter whether you have the correction calculation from the ophthalmologist (specialist for Ophthalmology) or have it carried out by an optician.
The advantage of the optician is the immediate production of the corresponding glasses or contact lenses. However, this should not be a reason to bypass the annual control of the eye function by the ophthalmologist (specialist in ophthalmology). Finally, one must not forget the many other causes of blurred vision / changes in visual acuity. So you can easily treat the symptom "problem with visual acuity", but to clarify other causes you should consult an ophthalmologist to be on the safe side. This applies to children (especially in whom visual blurring is noticed for the first time) and for people who are also familiar with other clinical pictures (e.g. Diabetes mellitus, high blood pressure, etc.) and also people who have problems with their visual acuity despite their glasses / contact lenses.
Forecast myopia
The myopia can be treated well using the therapy options listed above.
From the age of 30 comes the myopia usually comes to a standstill or only progresses very slowly. Even so, myopic people should get away from Ophthalmologist (specialist in ophthalmology) be examined, since myopia further dangers, such as a Retinal detachment to recover. Signs of this can be visual problems, e.g. in the form of soot rain or flashes of light and later also visual impairments in the manner of a curtain or a wall. Recognized in good time, the cause of such complaints can still be treated well.
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