Hypermetropie

Was ist Hypermetropie?

Hypermetropia (long-sightedness) is a refractive error and occurs when light from near objects is not quite brought to focus in time to hit the retina. The point of focus would in fact fall behind the retina, if the light could get that far.

The lens tries hard to change its thickness (becomes fatter or more rounded) in an attempt to bring the light into focus on the retina - a process called accommodation.

However, people with long sight cannot accommodate fully and so the light does not focus on the retina and vision is blurred. This occurs because the eyeball is too short, the cornea is too flat (and so bends the light rays less), or the lens cannot become round enough (and so lacks power).

People with a mild hypermetropia can usually see at distance, as this light does not need to be bent as much in order to focus it on the retina.

Their near sight may also be clear. However, they may get tiring of the eyes, often with a headache and vision discomfort, because the lens is having to work so hard. People with more severe hypermetropia are not able to see objects close to them clearly in focus.

Long sight means exactly what the term suggests: you can see objects which are a long distance from you quite clearly.

long sight

The diagram above shows the differences in focusing between a normal and a long-sighted (hypermetropic) eye.

Was ist ein Brechungsfehler?

Before we can understand hypermetropia, we need to understand refractive errors.

A refractive error is an eyesight problem. Refractive errors are the most common reason worldwide for reduced level of eyesight (visual acuity).

Augenquerschnitt

Unter Brechung versteht man die Beugung des Lichts, in diesem Fall durch das Auge, um es zu bündeln. Ein Brechungsfehler bedeutet, dass das Auge das Licht nicht richtig auf die Netzhaut bündeln kann. Dies ist in der Regel entweder auf Anomalien in der Form des Augapfels zurückzuführen oder darauf, dass das Alter die Funktionsweise der fokussierenden Teile des Auges beeinträchtigt hat.

Es gibt vier Arten von Brechungsfehlern:

• Short-sightedness (myopia).

• Long-sightedness (hypermetropia).

• Age-related long sight (presbyopia).

• Astigmatism (a refractive error due to an unevenly curved cornea).

Um Brechungsfehler vollständig zu verstehen, ist es nützlich zu wissen, wie wir sehen.

Patienten wählen aus für Visuelle Probleme

Gesundheit der Augen

Myopie

Der medizinische Name für Kurzsichtigkeit ist Myopie. Sehstörungen wie die Kurzsichtigkeit werden auch als Brechungsfehler bezeichnet. Kurzsichtigkeit führt zu unscharfem Sehen bei der Betrachtung von Dingen in der Ferne, während das Sehen in der Nähe normalerweise normal ist. Kurzsichtigkeit ist ein sehr häufiges Problem, das durch eine Brille, Kontaktlinsen oder eine Augenlaseroperation korrigiert werden kann.

von Dr. Philippa Vincent, MRCGP

When we look at an object, light rays from the object pass through the eye to reach the retina. This causes nerve messages to be sent from the cells of the retina, down the optic nerve, to the vision centres in the brain. The brain processes the information it receives, resulting in an image that we can see.

Fokussierung des Auges

Light rays come off an object in all directions, as they result from the light around us bouncing back off the object. The part of this bounced light that come into the eye from an object needs to be focused on a small area of the retina. If this doesn't happen, what we look at will be blurred.

Die Hornhaut und die Linse haben die Aufgabe, das Licht zu bündeln. Die Hornhaut leistet die meiste Arbeit, denn sie krümmt (bricht) die Lichtstrahlen, die dann durch die Linse laufen, die die Fokussierung fein justiert. Die Linse tut dies, indem sie ihre Dicke verändert. Dies wird als Akkommodation bezeichnet. Die Linse ist elastisch und kann flacher oder runder werden. Je runder (konvexer) die Linse ist, desto mehr können die Lichtstrahlen nach innen gebogen werden.

Die Form der Linse wird durch kleine Muskeln im Ziliarkörper verändert. Winzige fadenförmige Strukturen, die so genannten Ligamenta suspensiva, sind an einem Ende an der Linse und am anderen Ende am Ziliarkörper befestigt. Das ist ein bisschen wie ein Trampolin, bei dem die Linse der zentrale Hüpfer ist, die Suspensorien die Federn und die Ziliarmuskeln den Rand bilden.

Wenn sich die Ziliarmuskeln im Ziliarkörper anspannen, lockern sich die Aufhängebänder, wodurch die Linse dicker wird. Dies geschieht bei nahen Objekten. Beim Betrachten von Objekten in der Ferne entspannt sich der Ziliarmuskel, wodurch sich die Suspensoriumsbänder zusammenziehen und die Linse dünner wird.

Eine stärkere Beugung (Brechung) der Lichtstrahlen ist erforderlich, um sich auf nahe gelegene Objekte zu konzentrieren, z. B. beim Lesen. Für die Fokussierung auf weit entfernte Objekte ist weniger Lichtbeugung erforderlich.

What are the symptoms of hypermetropia?

The main symptom is a difficulty with near vision.

Other common symptoms of hypermetropia (long sight) include:

• 'Tiring' of the eyes (asthenopia).

• Kopfschmerzen.

• Uncomfortable vision.

• Difficulties seeing with both eyes (binocular vision).

• Lazy eye (amblyopia).

• Squint (strabismus).

Long-sighted people may have difficulty with depth perception (3-dimensional vision), as this needs two eyes to work together, more or less equally.

What causes hypermetropia?

The causes of hypermetropia (long sight) are usually hereditary (genetic). Long sight can occur at any age but it tends to become more noticeable above the age of 40 years.

In rare cases, long sight is caused by other conditions such as diabetes, small eye syndrome (microphthalmia), cancers around the eye and problems with the blood vessels in the retina.

Many babies and very young children tend to be slightly long-sighted but usually grow out of this by about 3 years of age.

A particular type of age-related long sight (presbyopia) occurs because the lens of the eye becomes more stiff with age.

Complications of hypermetropia

If severe hypermetropia (long sight) is present from a very young age, lazy eye (amblyopia) can result. The eye with less good vision does not learn to see properly because the brain ignores its signals and concentrates only on the better eye.

Visual development in the brain occurs in the first few years of life and if this problem is not spotted until after vision has finished developing, the poorer eye will not fully develop its 'information route' into the brain, so will never see as well.

What is the treatment for hypermetropia?

Brillen

The simplest, cheapest and safest way to correct long sight is with glasses. Convex prescription lenses (called plus lenses) are used to bend light rays slightly inwards to give a little bit of additional focusing power to the eye.

The light rays then have a lesser angle to bend travelling through the cornea and lens and the lens has less work to do. As a result, the light rays are able to focus on the retina. There is an enormous choice of spectacle frames available, to suit all budgets, faces, and personal styles.

Kontaktlinsen

These do the same job as glasses but they sit right on the surface of the eye. Many different types of contact lenses are available. Lenses may be soft or rigid gas-permeable.

They can be daily disposable, extended wear, monthly disposable, or non-disposable. Your optician can advise which type is most suitable for your eyes and your prescription.

Contact lenses tend to be more expensive than glasses. They require more care and meticulous hygiene. They provide good all-round vision and do not mist over (for example, while doings sports or in hot environments).

Sie erfordern jedoch mehr Pflege und sorgfältige Hygiene und sollten nicht beim Schwimmen, Duschen oder Schlafen getragen werden. Sie sind eher für ältere Jugendliche und Erwachsene geeignet als für sehr kleine Kinder.

Laser-Augenchirurgie

Laser eye surgery is an option for some people with long-sightedness. Generally, this type of surgery is not available on the NHS and can be expensive. Many private companies advertise laser eye surgery.

Complete and permanent resolution of the refractive error is possible in a number of people. Others have a significant improvement even though perfect vision is not achieved and glasses or contact lenses may still be needed.

These usually get better over time. Over-correction or under-correction of short-sightedness can also happen.

Complications include eye infection and dry eyes. Permanent loss of vision is very rare; if this happens, around 1 in 5,000 people need a corneal transplant to restore their vision. Up to 1 in 10 patients may need additional surgery to get the best result.

For more information, see the leaflet on Laser Eye Surgery.

Lens surgery

Refraktiver Linsenaustausch (RLE)

• In this procedure, your eye's natural lens is replaced by a clear synthetic implant called an intraocular lens (IOL). It is essentially the same process as modern cataract surgery.

• Multifocal IOLs aim to improve distance, intermediate, and close (near) vision, and can therefore be used to treat long-sightedness.

• RLE is suitable for people over the age of 50 years who have a prescription that is higher than the normal range for laser eye surgery. RLE can correct almost any level of long-sightedness. It is generally preferred in older people because, as you get older, your eye's natural lens becomes less flexible and less clear, so there is more benefit in replacing it. It also eliminates the need to have cataract surgery later in life. However, you should discuss with your operating surgeon which treatment option is best for you.

• The operation typically takes about 20 minutes per eye, is performed with eye-drop anaesthetics, and you can go home the same day. You can have both eyes done at the same time, or one eye at a time.

• Side-effects include eye discomfort, visual effects (such as blurring of vision, haloes around lights, and shadowing or shimmering arcs around the edges of vision), and subconjunctival haemorrhages. These usually get better over time.

• Permanent, serious loss of vision is much more common after RLE than after laser eye surgery. It affects approximately 1 in 500 patients. Other risks of the operation include bleeding, infection, and retinal detachment.

Wie oft muss ich mein Sehvermögen testen lassen?

Der NHS empfiehlt, dass die meisten Menschen ihre Sehkraft alle zwei Jahre untersuchen lassen sollten. Kindern werden routinemäßig Augenuntersuchungen in verschiedenen Phasen von der Geburt bis zum Schulalter angeboten.

People at higher risk of sight problems need more frequent eyesight checks. You should check to see what your optician or doctor recommends about regular check-ups if you have:

• Diabetes.

• Erhöhter Druck im Auge (Glaukom).

• Makuladegeneration.

• Or a family history of these conditions.

Menschen über 70 Jahre und Kinder, die eine Brille tragen, benötigen möglicherweise auch häufigere Augenuntersuchungen.

You should get your eyes checked if you notice any changes in your vision.

Einige Optiker bieten einen Hausbesuchsdienst an, um Sehtests für Menschen durchzuführen, die nicht in der Lage sind, sich auf den Weg zu machen.

Dr. Mary Lowth ist eine der Autorinnen oder die ursprüngliche Autorin dieses Merkblatts.