Introduction
Myopia can be corrected by wearing glasses or contact lenses. However, this does not directly correct the cause of myopia. Furthermore, a correction of myopia can be achieved by means of laser treatment.
In myopia, the eyeball is relatively too long. The incident light rays are not bundled in a point on the retina, but already before it, so that the rays that finally hit the retina are no longer centered in one point, but are already scattered again. As a result, the resulting image is blurred for the person concerned.
Glasses or contact lenses are made for short-sighted people with diverging lenses. These have a negative refractive value and ensure that the light rays entering the eye meet exactly on the retina in one point again. The short-sighted person then sees sharply again.
For this purpose, the person’s exact visual acuity is first determined by an eye test, so that the lenses or contact lenses can be made accordingly. There are many different types of contact lenses. There are daily lenses that have to be changed after one day, monthly lenses that can be worn for a month, and annual lenses.
There are also hard and soft contact lenses. In sensitive persons, however, wearing contact lenses can cause severe irritation of the conjunctiva and cornea. This results in reddened, dry or even itchy eyes.
Some people also describe a constant foreign body sensation in the eye. With increasing wearing time, the risk of conjunctivitis also increases. In addition, the lenses should not be worn while swimming or taking a sauna, because chlorinated water and intense heat will attack the lenses.
Orthokeratology
An alternative method to ordinary contact lenses are special lenses that are worn only at night. They lead to a flattening of the cornea, which improves visual acuity during the day. To achieve this, the lenses must be worn for about 6-8 hours per night, and no visual aids are needed during the day.
However, this only works for myopia of -4.5 diopters maximum. More pronounced myopia cannot be corrected with night lenses. A disadvantage of orthokeratology is that a decrease in visual acuity can occur at twilight and in the dark.
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