Myopia (short-sightedness)

Are there ocular diseases which cause myopia?

Small or medium short-sightedness is not a disease. High myopia with stronger tension of the retina and of the sclera is regarded as a disease and may be inherited. In addition, there are some diseases which cause myopia. For example, a temporary myopia can occur in diabetics. Also, a weakness of the lens fixating fibers or rupture of these fibers due to an accident with eyeball contusion leads to an increase in the refractive power of the lens and to myopia. Premature babies are often short-sighted, and a glaucoma (excessive intraocular pressure) during childhood causes myopia, as well, due to the long deformation of the eyeball.

In older people, a specific form of cataract (nuclear cataract) may occur, which progresses only very slowly and first does not lead primarily to opacification of the lens but more to an increase in its refractive power. As a result, these patients, who would usually need spectacles for near vision due to their old age and the related accommodative deficiency, suddenly can read again without spectacles - however, only for some time. This mistaken improvement of near vision is often used as proof for the success of miracle cures. The fact that the far vision of the patients deteriorates considerably, so that they need appropriate spectacles for far vision is neglected in such reports.

What can be done against myopia?

To "treat" myopia, that is to make it disappear, the prolonged eyeball would have to be shortened or the lens would have to be flattened. To shorten the eyeball would be a complicated operation which is out of the question due to the high risk. However, the cornea can also be flattened without surgery, namely with extremely flat fitted contact lenses which do not follow the corneal shape exactly, as is usual to make them comfortable to wear, but exert some pressure. However, the intended effect disappears after one to two weeks of removal of the lenses.

Another possibility of corneal flattening is offered by two different operation techniques:
In keratomileusis, a piece of the cornea is removed, deep-frozen, flattened with a lathe and repositioned. For the patient, the double operation is very strainous, but principally the method works. Unfortunately, scars cannot be avoided.

Keratomileusis:

A piece of the cornea is dissected (left side), lathed flat and sutured onto the cornea again (right side)

In radial keratotomy, 16 incisions are made into the cornea, which, however, may not penetrate completely. In this way, it will loose some stability and flatten in the center.

However, the result is not clearly predictable, because permanent changes in the corneal stability may occur within the lengthy scar formation process over years. Thus, the result achieved with the operation does not remain constant.

If no other complications occur, at least the visual acuity can be strongly impaired. In such cases, a corneal transplantation with all its problems would be required.

Therefore, this method to remove short-sightedness, which was developed in Columbia, cannot be recommended for European conditions, all the more as there are excellent possibilities of correction with contact lenses or spectacles in Europe, which do not exist in optotechnically underdeveloped countries.

Radial Keratotomie

Left: anterior view: Incisions into the cornea . . .

Right: . . . for lateral bulging due to tissue damage to flatten the corneal center (lateral view) 

 

In addition, corneal scars are not harmless. In favorable cases, they "only" cause an increased glare sensitivity especially when driving at night. The consequence would be a night driving prohibition. Furthermore, also late defects cannot be excluded.

Taking into consideration that only cosmetic reasons may be the cause for such an operation, since it can only be applied in low or medium myopias which can always be corrected very well with spectacles and contact lenses, it is obvious why German ophthalmologists judge the risk for their patients to be too high. Whoever absolutely dislikes spectacles can wear contact lenses as invisible visual aid. After this type of operations this will never again be possible, even though it would be necessary very often. The German Ophthalmological Society and the professional association of German ophthalmologists therefore refuse the radial keratotomy as an irresponsible operation.

Can relaxation training or "eye muscle training" fight myopia?

As early as 70 years ago, these exercises intended to make wearing spectacles superfluous were discussed for a while. Then they had fallen into oblivion for a long time, which does not suggest successful outcomes, because prior to, during and during the first time after the World War neither rather nice-looking spectacles nor well-tolerated contact lenses were available.

If the exercises had had the success promised by their inventor Dr. W. Bates at that time, their break-through would definitely have happened in the "bad days". However, they could not keep this promise, because

myopia cannot be trained away.

The eye is moved by six externally attached muscles. They are permanently active - also unvoluntarily, even during sleep - and due to the permanent change between tension and relaxation they are in a well-trained state without any additional training.

To influence myopia, these muscles would have to shorten the prolonged eyeball by a simultaneous lateral outside tension (against the ear and the nose). Not only anatomically speaking this is not possible. Even if the muscles - like in several diseases - are under excessive pressure, such as in Basedow´s disease, where the eyes are strongly displaced forward, the shape of the eyeball and thus also short- or far-sightedness do not change at all. On these grounds, Bates theory that the external eye muscles might exert an influence on myopia is a heresy.

Several defenders of Bates exercises intend to remove myopia by relaxation of the orbicular muscle. However, only accommodation, that is near vision, is controlled by this muscle. A normal-sighted eye is adjusted to far-vision in a relaxed state and will create a sharp image. The short-sighted (prolonged) eye will always see everything behind a short distance from the eyes blurred, simply because the image does not arrive on the retina but in front of it. The fact that the relaxation of the orbicular muscle has no stronger effect on short-sightedness than any other ocular muscle becomes clear by merely looking at the examination method used by ophthalmologists with a suspicion of myopia. Here, drugs are used to completely relax the inner orbicular muscle, because short-sightedness can be reliably detected in this way. If Bates was right, myopia would have to disappear during the ophthalmological examination - for the time the drug-induced muscle relaxation continues.

"Relaxation exercises" and "eye muscle training" cannot influence short-sightedness - this was also definitely found by ophthalmologists who, disregarding all theoretical concerns, tried this exercising method in their patients. Where the promises of the defenders of Bates´ theory are only fraud, they become a criminal deed when short-sighted patients are driving without spectacles because they believe their vision is improved after the "exercises". They should better think of their responsibility for others, when driving or working!

How can myopia be optically corrected?

There are two possibilities:

Spectacles or contact lenses (see figures)

Do you spoil your eyes with spectacles or contact lenses?

No! If at all, you "spoil" yourself. Who had a good vision once will not very likely like to do with poorer vision. Regarding changes in the visual acuity you should never forget that the eye is growing like any other organ. Sometimes its growth phase has not been entirely completed when the body has already reached its final height. Therefore, an increase in myopia can never be due to the negative influence of auxiliary visual means but only originates from a natural increase in the size of the eyeball. Every single millimeter results in as many as 3 diopters, so that even the smallest growth must take effect.

Can contact lenses stop an increase in short-sightedness?

Several contact lens fitters continue to claim this and try to prove it with few examples. However, no scientific proof of the efficacy of the method to influence a progression of the myopia with very flat fitted contact lenses could be found to date.

Should the visual acuity in myopic eyes be controlled more frequently?

Yes! And more than that. You should have your eyes examined regularly as suggested by your ophthalmologist.

Short-sightedness is a deviation from the standard "emmetropia" or the consequence or symptom of a disease to be found and treated to maintain the possibly endangered vision. Furthermore, in the presence of myopia more frequently "thinner areas" of the retina originate due to its tension, which may lead to retinal tears followed by retinal detachment. When diagnosed in time, they can be easily reattached - e.g. with a laser, and the hazard of blindness is mostly under control.

[Translate to English:] Gibt es Augenkrankheiten, die Kurzsichtigkeit hervorrufen?

[Translate to English:] Geringe und mittlere Kurzsichtigkeit ist keine Krankheit. Hochgradige Kurzsichtigkeit mit stärkerer Dehnung der Netzhaut und der Lederhaut gilt als Krankheit und kann erblich sein. Daneben gibt es einige Krankheiten, die Kurzsichtigkeit erzeugen. So kann z.B. bei Diabetikern eine vorübergehende Myopie auftreten. Auch eine Schwäche Linsen- Aufhängefasern oder deren Zerreißen nach einem Unfall mit Augapfelprellung führt zu einer Steigerung der Linsenbrechkraft und zu Myopie. Frühgeborene sind oft kurzsichtig, und ein Grüner Star (zu hoher Druck im Auge) in der Kindheit verursacht ebenfalls durch längliche Verformung des Augapfels eine Kurzsichtigkeit.

Bei älteren Menschen kann eine besondere Form des Grauen Stars (der Kernstar) aufreten, der nur ganz allmählich fortschreitet und zunächst weniger eine Trübung der Linse als ein Verstärken ihrer Brechkraft bewirkt. Dies wiederum hat zur Folge, daß diese Patienten, die Aufgrund ihres Alters und der damit verbundenen mangelnden Akkommodationsfähigkeit für die Nähe eine Brille bräuchten, auf einmal wieder ohne sie lesen können- allerdings nur vorübergehend. Diese vermeintliche Besserung des Nahsehens wird gern als Beweis für den Erfolg von Wungerheilmethoden dargestellt. Die Tatsache, daß die Patienten in der Ferne sehr viel schlechter sehen und eine entsprechende Fernbrille benötigen, verschweigen solche Berichte.

Myopia - what is it?

Myopia is the medical name for short-sightedness.

Short-sighted means that near objects are focused perfectly sharp, but not those at a greater distance. Thus, the short-sighted eye is not principally "worse" than the emmetropic eye, since it can be clearly superior in the short range.

If the eye is compared with a camera, cornea and lens form the objective and the retina is the film. The difference between a short-sighted and a normal-sighted eye is only the coordination between the refractive power of cornea and lens and the distance to the "plane of the film", that is the retina.

Carrying on this thought, a short-sighted eye can be compared with a camera with its objective set to the short-range focus. In relation to the refractive power, it has a greater distance from the film plane compared to the setting for a distance shot.

The same applies for the short-sighted eye: Also here, the distance to the retina related to the refractive power of the cornea and the lens is greater compared to an emmetropic eye. The human eye is able to change the refractive power of its lens. It adjusts to the respective distance where a sharp image is desired. If the focused object is near - e.g. during reading - stronger bending of the lens is required. This process is called accommodation.

In contrast to normal-sighted eyes, the myopic eye does not have to fully accommodate, since the sharpest vision exists in the near range anyway. If it does nevertheless, the effect of its short-sightedness is increased for the duration of the accommodation. In this way, the distance between the eye and the object can be reduced and finer details can be seen more clearly than it would be the case with a normal-sighted eye.

In contrast, a sharp far-distance image cannot be achieved by accommodation. A normal-sighted person has it by nature, the short-sighted patient needs visual aid with divergent lenses to transport the image onto the retina in contrast to the situation without appropriate correction with spectacles or contact lenses, where the image is created more anteriorly, in the vitreous.

The ability to accommodate decreases during the entire lifetime in all humans. This is experienced especially in the middle of the fifties, when the near point is growing outside the usual reading distance. Since short-sighted persons first depend less on it than normal-sighted ones, they need pulpit spectacles or a corresponding addition to far vision spectacles somewhat later - depending on the degree of myopia.

© Copyright 2000 Berufsverbandes der Augenärzte Deutschlands (BVA) und Deutschen Ophthalmologischen Gesellschaft (DOG)