Short-sightedness and long-sightedness – clear vision without glasses and contact lenses?

Seeing is one of the most complicated processes in our body. Thanks to the perfect interaction of the  cornea , lens, retina, vitreous body, optic nerve and finally the brain, we are able to see and understand an image. But almost every second German has problems seeing. Read what short-sightedness and far-sightedness are and whether, for example, laser surgery is an alternative to  glasses  and contact lenses.

The yellow spot

The focal point, also known as the “yellow spot” or fovea centralis , is located on the retina of the eye   . Ideally, this is exactly where the light rays hit through the lens – you can see everything sharply. However, almost every second German has limited vision, is short-sighted or far-sighted. The lens of the eye cannot adjust itself correctly from close to long-distance vision – or vice versa.

myopia and astigmatism

Anyone who has trouble seeing at a distance suffers from  short-sightedness , also called  myopia  . The cause is usually an eyeball that is too long or the refractive power of the cornea that is too strong: this is where the light rays meet in  front  of the retina, which means that a sharp image cannot form on the retina. Distant objects are recognized less well than close ones.

It is noticeable that short-sighted people often squint their eyes. As a result, the lid gap becomes narrower and the pupil diameter smaller and only the central beam path can pass through.

There are two types of myopia:

• the so-called school myopia ( myopia simplex ), which occurs between the ages of ten and twelve. It comes to a standstill around the age of 25.
• The progressing myopia ( myopia progressiva ), on the other hand, is getting worse and the patient often has severe visual impairments of up to -15 dioptres and more. The retina is also greatly stretched, sometimes even detaching.

What is a diopter?

The physical unit diopter refers to the refractive power of an optical lens, for example the eye. If the eye is short-sighted, the diopter values ​​are preceded by a minus sign (-). In the case of farsightedness, the values ​​are given with a plus sign (+).

astigmatism

In addition to short-sightedness, there is often  astigmatism , also known as astigmatism. It is caused by an uneven curvature of the corneal surface. The normal cornea is hemispherical like the lens of a camera. Therefore, vertical and horizontal lines are displayed sharply.

If the cornea is not hemispherical but rather elliptical in shape, the image will be distorted. A point is not displayed as a point, but as a small line.

farsightedness 

In the case of long-sightedness, experts also refer to it as oversightedness,  hyperopia  or  hypermetropia  , the eyeball is a bit too short, and sometimes the refractive power of the eyes is too low.

If you look at an object up close, the far-sighted eye is unable to focus the light sufficiently. The refractive power of the eye is not sufficient, the sharp image only  emerges behind  the focal point. Only a blurred image is formed on the retina.

The light that reaches the eye from a distance, on the other hand, can be bundled normally. As soon as you get closer to people or objects, the image that was still sharp in the distance becomes blurred.

Eye pain and headaches  are the most common complaints associated with long-sightedness  . This is related to the long-term use of the ciliary muscle: the ciliary muscle controls the stretching of the lens, which changes the refractive power. In addition, there is rapid eye fatigue or blurred vision.

presbyopia

As people get older, many people feel that their arms have become too short when reading – the letters become blurred close to the eye. Presbyopia, technically known  as presbyopia  , occurs when the elasticity of the lens decreases. From around the age of 40 to 45, the lens and the circular muscle in the eye lose their elasticity and focusing becomes imprecise. 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 adding the appropriate correction value. Under certain conditions, however, short-sightedness and far-sightedness can be corrected with the help of so-called refractive eye surgery, in which the refractive power of the eye is changed by a certain amount.

Refractive procedures are various procedures for the surgical correction of ametropia such as nearsightedness, farsightedness and astigmatism. Ophthalmologists have been using laser technology to treat ametropia since the early 1960s.

Photorefractive keratectomy (PRK) is a laser procedure that is used to ablate the cornea. The center of the cornea is about 0.5 mm thick and its edge about 1 mm. Using the laser, an approximately 0.1 mm thick part of the central cornea is then abraded to compensate for the ametropia. A disadvantage of PRK is the slow healing and the sometimes significant pain after the  operation .

The LASIK method

In 1993, however, came the breakthrough with the invention of the so-called LASIK technique – an abbreviation for  laser in situ keratomileusis  – in English “laser ablation inside the corneal tissue” – probably the most widely used laser technique today.

Well over 100,000 patients in Germany are operated on with this method every year; the success rate depends on the diopter number. 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-Augen-Laser-Klinik (private clinic for laser eye surgery) in Fürth, classified as a suitable surgical correction procedure for people who are correcting short-sightedness up to -10 dioptres or astigmatism up to 3 dioptres and far-sightedness up to + 3 dioptres – but presbyopia cannot be improved in this way.

process during the operation

The cornea of ​​the eye is cut flat under local anesthesia. In this way, the upper, curved piece of the cornea can be folded back like a small lid. This is where the work with the laser begins:

The excimer laser is a cold-light laser in the invisible ultraviolet spectrum that penetrates just a few thousandths of a millimeter into the corneal tissue and removes it – all of this is computer-controlled. The corneal cover is then closed again and the corneal disc protects the wound like an endogenous plaster, allowing it to heal undisturbed.

The whole operation takes a maximum of ten minutes. However, health insurance companies only pay the quite high costs of around 2,000 euros per eye in exceptional cases.

However, laser correction should generally be discouraged if the patient is under the age of 18, if the ametropia is constantly changing, in the case of  cataracts  and chronic corneal diseases as well as systemic immune diseases.

operations on the lens

The lens of the eye can also be operated on (without a laser) – around 800,000 patients in Germany are treated every year for cataracts, a clouding of the lens of the eye, mostly from the age of 60. The cloudy eye lens is removed and replaced with an artificial clear eye lens.

The implantable contact lens represents an alternative for high refractive power errors, i.e. nearsightedness from -10 to -20 dioptres and farsightedness from +5 to +8 dioptres. It is particularly useful when the cornea is too thin.

A special artificial lens is placed inside the eye, between the iris and the lens of the eye, in the so-called posterior chamber. The body’s own lens also retains its close focus ability. The cornea is usually left untouched during this procedure.

Long-term experience with this surgical method is still lacking. In around 90 percent of cases, everyday life should be possible without glasses. These results are in some cases significantly worse when correcting farsightedness or astigmatism. After the operation, it is necessary to take eye drops for several months to prevent scarring of the cornea.