myopia

Myopia: description

Myopia is a congenital or acquired ametropia of the eye. Those who are short-sighted can usually still see well in the vicinity, while objects in the distance appear blurry (in the case of the farsighted, it is just the opposite). A short-sighted person does not generally see worse. At close range, he may even be superior to a normal sighted person. How pronounced the ametropia is, is measured in diopter (dpt). Short-sighted is someone with a negative reading, and the more so, the higher the number is after the minus. A reading of -12 D, for example, describes a high-grade myopia, ie a strong myopia.

Strictly speaking, myopia is usually not at all a disease. Up to an ametropia of minus six dioptres, it is only an anomaly, ie a deviation from the average value. It is only with severe ametropia that pathological (pathological) myopia is present.

The proportion of shortsighted people in different age groups varies. According to the Federal Statistical Office, there are nearly four times as many nearsighted as far-sighted people up to the age of 40 years. Thereafter, the proportion of farsighted people increases. From the age of 50, almost twice as many people are visionary as short-sighted. Hyperopia tends to be more common in older people, while nearsightedness is more common in children and young people. Men are a little less likely to be ill than women.

Myopia simplex and Myopia maligna

Experts distinguish a Myopia simplex (simple myopia) from a Myopia maligna (malignant myopia):

The Myopia simplex is also called school myopia. It starts at school, usually around the tenth to twelfth year of life. It can worsen in the following years, in order to stay stable after the age of 20 most of the time. Most sufferers achieve with this form of myopia dioptres of at most -6 dpt. In a small part, myopia can worsen to -12 D and stabilizes until the age of 30.

Myopia maligna, on the other hand, progresses further into adulthood. It therefore has real disease value.

Myopia in children

Children of nearsighted parents are also more likely to suffer from nearsightedness. This suggests that myopia also has a hereditary component. Short-sighted parents should therefore have their children examined by an ophthalmologist as soon as possible. He can diagnose myopia in the first year of life. At least in preschool age an eye examination should take place. Good vision is important for the healthy development of the child. In addition, playing outdoors or participating in road traffic with untreated myopia can be dangerous. Whether eyeglasses or contact lenses are suitable as a visual aid for your child, the ophthalmologist can discuss with you. A properly adjusted glasses does not deteriorate the eyes. If shortsightedness progresses due to growth, this can not be prevented with or without glasses.

Myopia: symptoms

Short-sighted eyes are focused on near vision and in this area sometimes even sharper than people with normal vision. Short-sighted people can not focus on an object in the distance. He therefore appears blurry. The distance a short-sighted person can see well depends on his or her prescription: Affected persons with a diopter of -1 dpt can see objects up to one meter in focus. People with -12 D only objects in about eight centimeters away.

Myopia can cause other symptoms in addition to the impaired vision. In the course of life the vitreous liquefies in the eye. In myopia, this often happens faster than with normal sightedness. Swimming Streaks in the vitreous can cause those affected to see shadows in the field of vision.

In addition, a strong myopia may favor other diseases. For example, the aqueous humor can flow off worse. This increases the intraocular pressure, open-angle glaucoma may occur in which the optic nerve is damaged. In malignant myopia, the retina can be stretched so much that it dissolves more easily (retinal detachment). As a result, seeing can suddenly worsen.

Myopia: causes and risk factors

In vision-impaired people, the refractive power of the eye does not match the distance of the retina. For a better understanding, one can compare the eye with a camera: the lens corresponds to the cornea and lens. The retina can be compared to the film. Incident light rays are refracted by the cornea and lens and focused in one point. At this point, a sharp picture is created. To be able to perceive it, this point must be at the retinal level.

In order to be able to clearly see both near and distant objects, the eyes have to change (accommodate) their refractive power. For this purpose, the shape of the eye lens, which is responsible for the refraction of light rays, modified by muscle power: If the eye lens lengthened, it is flatter – their refractive power decreases. Then she can clearly depict distant objects. On the other hand, a lens that is less taut, ie more spherical, has a greater refractive power – close objects can now be sharply imaged.

In myopia, there is a mismatch between the refractive power of the eye and the length of the eyeball: When looking into the distance, the rays of light do not meet on the retina even when the lens is relaxed, but already slightly ahead, so that they only produce a blurred image.

For the mismatch between refractive power and axial length in myopia can be different causes. Mostly there is an axis myopia. The eyeball is longer than normal eyes and the retina is further away from the cornea and lens. An eyeball just one millimeter longer can have a myopia of -3 dpt. cause. In rare refractive myopia, the eyeball is normally long, but the power of the cornea and lens is too strong (perhaps because the radius of the cornea is unusually small or the lens refractive power is altered due to diabetes or cataract).

Risk factors for myopia

There are some diseases that are more likely to cause nearsightedness, such as diabetes (diabetes mellitus), when blood glucose levels are poor. Normalization of blood sugar can make myopia disappear again.

Also a form of cataract (the so-called core star) can favor a shortsightedness. It often occurs in the elderly: even before they notice the lens opacities, sometimes they can suddenly read again without reading glasses. The cataract can temporarily improve the near vision by the also occurring myopia, but the distance vision deteriorates.

In some disease syndromes, a (strong) myopia often occurs. The diseases are partly genetic and can be inherited. These include, for example, Marfan syndrome and Down’s syndrome. Here, in addition to myopia, symptoms also occur in other organs.

Myopia in children is favored by a premature birth.

In some cases, myopia is the result of an accident in which the lens fibers have become loose or torn.

Myopia: examinations and diagnosis

The right contact person for myopia is an ophthalmologist. He could ask you the following questions at the first meeting:

• When did you notice a vision deterioration?
• Has this occurred suddenly or creeping?
• When does your vision deterioration affect the most?
• How is the visual impairment expressed? (Blurred vision? Color vision problems?)
• When was your eye last examined?
• Do you suffer from other illnesses such as diabetes?
• Are other people short-sighted in your family?
• Are there hereditary diseases in your family?

Then he will ask you to look into a device for a distant object (often a colored cross). While the device measures the power of the eye, you should keep your eyes open. In addition, your ophthalmologist will ask you to read a series of different numbers or letters on the wall. Sometimes different lenses are held in front of the eye. The ophthalmologist asks you if the picture will get sharper. He also looks into your eyes with a bright light and a magnifying glass. Sometimes it is necessary to dilate the eyes with special eye drops before the examination. Afterwards, you will still see blurred spots for a while and may therefore not be allowed to drive for a few hours.

A comprehensive eye exam includes more methods. For example, to check spatial vision, the ophthalmologist will show you cards that seem to have an object coming out of the card. You must also specify whether you perceive a box pattern as straight or curved. To rule out color vision problems, you must recognize numbers or patterns of dots of different colors.

Since myopia sometimes leads to increased intraocular pressure, the doctor advises to make an appropriate measurement. Since myopia can cause further eye changes, sufferers should have their ophthalmologist examined about once a year.

Myopia: treatment

With different methods one can improve the myopia. Spectacle lenses or contact lenses compensate for ametropia. Surgery can even cure myopia in certain cases. Combining several methods, high grade myopia can often be treated well.

Glasses in myopia

With “minus lenses” of glasses you can improve myopia. The light rays that strike the eye, which already meet in front of the retina during myopia, are scattered through the lens so that they only meet directly on the retina. For this purpose, the lens is slightly thicker at the edge than in the middle. Thanks to modern technology, spectacle lenses can be ground very thin today.

Up to a prescription of -8 D, the glasses are the most common visual aid. It offers some advantages: If myopia changes, glasses can be readjusted at any time. This treatment is therefore particularly suitable for children whose eyeballs are changing in growth. In addition, glasses are suitable for people who need to read a different setting than for the distance. With a progressive lens both needs can be realized in a spectacle lens. In addition, a pair of glasses is very gentle on the eye. Nevertheless, some people feel a pair of glasses as annoying.

Contact lenses for myopia

Contact lenses are an alternative to glasses for many short-sighted. They are small transparent lenses made of soft or hard plastic. Which type of contact lens is suitable for you personally, an ophthalmologist can determine.

One of the advantages of contact lenses is that they are invisible and do not fog up. Because they are placed directly on the eye, they correct the visual acuity in the entire field of view. Above all, athletes prefer to wear contact lenses rather than glasses. The lenses (as well as glasses) can be easily adapted to a new vision. In case of pronounced myopia, contact lenses are also popular because they do not reduce the size of the picture, unlike the strong negative lenses of a pair of glasses. This effect is relevant from a prescription of -3 dpt.

For short-sighted people with early onset presbyopia, there are contact lenses with different eyesight (similar to a progressive lens). However, these are not suitable for any form of myopia.

Contact lenses require good hygiene. To prevent eye infections, they must be cleaned regularly. In addition, contact lenses must not be worn indefinitely. Under a contact lens, the eye is in fact supplied with oxygen less. In some people’s eyes are irritated (for example, after too long wearing time, with dust in the air or dry heating air). They are red and hurt.

Contact lenses for the night (orthokeratology)

In certain forms of myopia, special rigid (hard) contact lenses can be worn at night. They exert a certain amount of force on the cornea, causing the cornea to flatten after some time. This compensates for myopia, even during the day. However, the effect diminishes during the course of the day, so you may need to use lenses or put on glasses. These lenses may be an alternative for myopia who, for example, can not tolerate contact lenses during the day due to dust or irritants.

Operative correction of myopia

There are also surgical therapies for myopia: lasers. Here, the cornea is flattened permanently with a laser. Depending on the exact methodology, a distinction is made between different methods. They are called photorefractive keratectomy (PRK), LASIK or LASEK. Eye-laser is not suitable for everyone concerned. It can be used up to a near-sightedness of -6 dpt. At best, the doctor can cure myopia.

In addition, corrective lenses can be implanted in the eye to compensate for myopia. This procedure is mostly used only for severe myopia, as it can limit the ability of the eyes to accommodate themselves, ie their adaptability from near to far vision and vice versa. In some cases of myopia, your own lens is replaced by an artificial lens. The operation is similar to a star operation.

Each of these operations involves certain risks that the physician should discuss with the patient in advance. Cortisone drops after the operation should prevent the formation of scars that limit vision. If exposed nerve endings are damaged during surgery, pain is possible.

Whether myopia can really be cured by surgery is different. One hundred percent safety can not be given before the operation. Eventually, the affected person is still dependent on visual aids after the procedure. Eyesight deteriorates after the operation or if presbyopia occurs, visual aid is also necessary.

Myopia: eye training

There is no reason that myopia can be prevented or improved through eye training. This erroneous belief assumes that the eyes must be consciously exercised and relaxed to recover from their ametropia. In fact, our eye muscles are in the best training condition even without special exercise. Since the different muscles move the eyes partially in opposite directions, some muscles are always relaxed. Under no circumstances can myopia be positively influenced by eye training.

Myopia: disease course and prognosis

Myopia often develops in childhood. In the course of growth, it can both improve and worsen. Most of the time myopia does not change much after age 20.

With increasing age, the eyes can generally accommodate worse. The ability of the lenses to optimally adjust to far and near vision decreases already from the age of 25 years. From the age of 40, many people eventually become old-sighted and need reading glasses. In myopia, however, the eyes are set anyway on the near vision. Short-sighted people often need reading glasses only later or never at all.

There myopia If other ocular conditions are present, eyes should be examined regularly by the ophthalmologist.