With short-sightedness, people only see sharply in close proximity. It cannot be cured, but can be corrected with glasses, contact lenses or laser treatment.
What is myopia?
Ophthalmologists distinguish four forms of ametropia: myopia, hyperopia, astigmatism and presbyopia. Most people are short-sighted.
Experts refer to myopia as myopia. The word is derived from the Greek word “myopia” and means “blinking face”. In fact, near-sighted people blink more often to see things at a distance. Near-sighted people only see sharply at short and very short distances.
The degree of myopia is expressed in diopters (dpt). The unit of measurement describes how much light a lens must refract in order to correct the defective vision. Negative dioptre values stand for myopia, positive values for hyperopia. The higher the value, the stronger the correction must be and the worse the vision of those affected without visual aids.
Distribution: How many people are nearsighted?
Between 15 and 49 percent of the German population is nearsighted, including many children and young people. Experts expect that by 2050 at least every second person in Western Europe will have difficulty seeing clearly at a distance.
For the World Health Organization (WHO), myopia is already one of the five most important eye diseases that must be curbed. This is because it causes serious eye conditions such as macular degeneration, retinal detachment and glaucoma.
Forms of myopia:
Ophthalmologists speak of pathological or high myopia when the vision of the eye is weakened by at least -6 diopters. Due to the elongated eyeball, the retina and choroid are particularly tense. As a result of the stretching, the retina can become loose or tear, sag and scar. Microfractures in the retina cause vessels to proliferate and impair vision. Experts also speak of myopic maculopathy. In 2050, one in ten people in this country is expected to have pathological myopia.
The so-called malignant or malignant myopia is rare. However, the eyeball grows so extremely that people have a visual impairment of up to -30 diopters. Various structures of the eye are particularly susceptible under such extreme conditions: above average, the retina detaches itself more often than the eye itself. The yellow spot, also known as the point of sharpest vision, is more often damaged. Those affected can even go blind. Malignant myopia is hereditary. Currently, one to three percent of the population suffer from this dangerous form of myopia.
If one eyeball has grown normally and the other is elongated, one is short-sighted in only one eye. Eyeballs of different lengths result in different dioptre values for the two eyes.
What are the causes of myopia?
Nearsightedness can be better understood by imagining the eye as a camera. Cornea and lens form the lens, the retina is the film. Lens and cornea refract the incoming light rays, the reduced image is created on the retina.
Near-sighted people usually have an elongated eyeball. This means that the image is not created directly on the retina, but in front of it. An eyeball extended by one millimeter already leads to a myopia of -2.7 diopters. The longer the eye is, the greater the blurriness and visual impairment.
A rare reason for myopia is refractive myopia. Here, the lens, aqueous humour and cornea are altered in such a way that the focal point of the light rays is imaged in front of the retina. The eyeball is usually normal.
How does myopia develop?
That the eyeball grows excessively is hereditary. About ten to 15 percent of children are nearsighted when one parent is also nearsighted. The risk increases threefold if both parents have poor vision at a distance.
Lack of daylight and short visual distances stimulate the eyeball to grow. Today’s widespread visual, learning and leisure-time behavior plays a major role in the fact that myopia is on the increase. Instead of spending a lot of time in the fresh air, a large part of everyday life takes place indoors. A constant glance at a tablet, smartphone or computer screen prevents restful distance vision.
New technologies are the main reason why almost all young people in Asian countries like China are short-sighted. Reading under the comforter with a flashlight can also increase myopia.
What are the symptoms of myopia?
In most cases, myopia becomes apparent when the children go to school. They no longer recognize the writing on the blackboard well or have difficulty deciphering advertising lettering, posters or screens in the distance.
Nearsighted people also attract attention by blinking or squinting their eyes a lot. This causes the eyelid gap to narrow. Less light rays penetrate the pupil. The bundle of rays becomes smaller and hits another point – in the best case directly on the retina.
Headaches with myopia
For the eyes it means stress to continuously compensate the visual defect and to focus the image. Near-sighted people tense numerous muscles of the head and face as well as the neck when squinting and blinking. This causes headaches.
How quickly does myopia deteriorate?
You do not become nearsighted from one day to the next. As the child grows, the eye becomes longer. At the same time, however, the corneal refractive power decreases until the age of twelve, so that the light rays initially remain on the center of the retina. If the eyeball then continues to grow, myopia develops. Due to this phenomenon, myopia also increases in adolescence to early adulthood. According to studies, myopia is most widespread among 24-year-olds.
How quickly myopia progresses depends, among other things, on visual habits and genetic preconditions. Normally, the eyeball stops growing between 25 and 30 years of age. If you want to have your eyes lasered, it is better to wait until the dioptre value is constant for two years.
Diagnosis of myopia
Ophthalmologist or optician diagnose myopia by means of an eye test. He checks whether pathological changes in the eye are hidden behind the harmless ametropia. Depending on the findings, he will arrange for further tests, such as measuring the intraocular pressure or examining the eye with a slit lamp.
During the eye test, the specialist checks the vision at a distance. To do this, he uses vision panels that are suspended five to six meters away. They display numbers, E-hooks or Landolt rings. The patient must recognize the numbers or indicate in which direction the ring or E is open. One eye is covered in each case. The eye to be tested is checked by a specialist with and without corrective glass.
An eye test can vary depending on the light conditions and the time of day. The visual acuity is reduced by about half when it is twilight. In the dark, we can only see with one-tenth of the daytime visual acuity.