Seeing is one of the most complicated processes in our body. Through the perfect interaction of the cornea, lens, retina, vitreous, optic nerves and finally brain, we are able to see and understand a picture. But almost every second German has problems seeing. Read what short-sightedness and hyperopia are and whether, for example, laser surgery is an alternative to glasses and contact lenses.
The yellow spot
On the retina of the eye is the so-called focal point, also called "yellow spot" or fovea centralis . This is exactly where the light rays ideally strike through the lens - you can see everything in focus. Almost every second German, however, has a limited vision, is short-sighted or far-sighted. The eye lens can not adjust properly from near to far view - or vice versa.
Myopia and astigmatism
Those who have problems with seeing in the distance suffer from myopia, also called myopia . The cause is usually a too long eyeball or too much refractive power of the cornea: here the rays of light meet in front of the retina, therefore no sharp image can arise on the retina. Distant objects are less well recognized than close.
It is noticeable that nearsighted people often squint their eyes. As a result, the eyelid gap becomes narrower and the pupil diameter becomes smaller and only the central beam path can be transmitted.
There are two types of myopia:
- the so-called school myopia ( Myopia simplex ), which occurs between the tenth and twelfth year of life. She comes to a halt around the age of 25 years.
- The progressive nearsightedness ( Myopia progressiva ), however, is getting worse and the patient often has severe vision problems down to -15 diopters and more. Also, the retina is stretched greatly, sometimes it even dissolves.
What is a diopter?
The physical unit diopter denotes the refractive power of an optical lens, for example the eye. If the eye is nearsighted, there is a minus sign (-) in front of the diopter values. For long-sightedness, the values are indicated with a plus sign (+).
In addition to myopia, there is often astigmatism, also called astigmatism . It is caused by an uneven curvature of the corneal surface. The normal cornea is - like the lens of a photo camera - hemispherical. Therefore, vertical and horizontal lines are displayed sharply.
If the cornea is not hemispherical, but rather elliptical in shape, the image is distorted. A point is not depicted as a point, but as a small line.
In the farsightedness, experts also say clarity, hyperopia or hypermetropia to it, the eyeball is advised a bit too short, sometimes the refractive power of the eyes is too low.
When looking at an object close up, the farsighted eye does not succeed in focusing the light strongly enough. The refractive power of the eye is not sufficient, only behind the focus creates the sharp image. The retina produces only a blurred image.
The light that reaches the eye from a distance, however, can be bundled normally. As soon as one gets closer to people or objects, the image, which was still sharp in the distance, blurs.
In farsightedness, eye and headaches are the most common complaints. This is related to the continuous stress of the ciliary muscle: the ciliary muscle controls the stretching of the lens, which alters the refractive power. In addition, there is a rapid fatigue of the eye or blurred vision.
With age, many people feel that their arms have become too short while reading - the letters are blurred close to the eye. Presbyopia, termed presbyopia, occurs when the elasticity of the lens decreases. From around the age of 40 to 45, the lens and the sphincter in the eye lose their elasticity and the focus becomes inaccurate. Reading glasses are now inevitable.
Alternative to contact lenses and glasses: laser surgery
Contact lenses and glasses temporarily compensate for ametropia by reducing or increasing the refractive power of the eye by preceding the corresponding correction value. However, short-sightedness and hyperopia can be corrected under certain conditions with the aid of so-called refractive eye surgery, by changing the refractive power of the eye by a certain amount.
Refractive procedures are various procedures for the operative correction of ametropia such as shortness, farsightedness and astigmatism. Since the early 1960s, ophthalmologists have been using laser technology to treat ametropia.
Photorefractive Keratectomy (PRK) is a laser procedure used to abrade the cornea. The center of the cornea is about 0.5 mm thick, its edge about 1 mm. By means of the laser, an approximately 0.1 mm thick part of the central cornea is now abraded to compensate for ametropia. A disadvantage of the PRK is the slow healing and the sometimes significant pain after the operation.
The LASIK method
In 1993, however, the breakthrough came with the invention of the so-called LASIK technique - an abbreviation for Laser in situ keratomileusis - to German "laser ablation inside the corneal tissue" - probably the most widely used laser technique today.
Well over 100, 000 patients in Germany can be operated on annually with the method; the success rate depends on the diopter. The lower the number, the higher the success rate. In general, the success rate is between 97 and 99 percent. It is scientifically recognized and according to Dr. Martin vom Busch, senior physician at the Euro-Eye Laser Clinic in Fürth, Germany, is considered a suitable surgical correction procedure for people with short-sightedness up to -10 dioptres or astigmatism up to 3 diopters and hyperopia up to +3 dioptres but the presbyopia can not be improved that way.
Operation at the surgery
Under local anesthetic, the cornea of the eye is cut flat. Thus, the upper, arched piece of the cornea can be folded back like a small lid. Here begins the work with the laser:
The excimer laser is a cold light laser in the invisible ultraviolet spectrum, which penetrates only a few thousandths of a millimeter into the corneal tissue and this ablates - all computerized. Subsequently, the corneal lid is closed again and the corneal disc protects like a body-own patch the resulting wound, which can heal so undisturbed.
The whole operation takes a maximum of ten minutes. However, health insurance companies pay the rather high costs of around 2, 000 euros per eye only in exceptional cases.
However, a laser correction should always be discouraged if the patient is under 18 years old, if the ametropia is constantly changing, in cataracts and in chronic corneal diseases and systemic immune diseases.
Operations on the lens
The eye lens can also be operated on (without a laser) - in Germany, for example, around 800, 000 patients a year are treated for cataracts, and a clouding of the eye lens usually from the age of 60 years. Here, the cloudy eye lens is removed and replaced with an artificial clear eye lens.
The implantable contact lens is an alternative for high refractive errors, ie myopia from -10 to -20 diopters and hyperopia from +5 to +8 dioptres. It is especially useful when the cornea is too thin.
A special artificial lens is inserted into the interior of the eye, between the iris and the eye lens, into the so-called posterior chamber. The body's own lens will continue to retain its Naheinstellungsfähigkeit. The cornea is normally unaffected by this procedure.
Long-term experience with this surgical method is still missing. In about 90 percent of cases a life in everyday life without glasses should be possible. These results are sometimes significantly worse for correction of farsightedness or astigmatism. After the operation, it is necessary to take eye drops for several months to prevent scarring of the cornea.