Hypermetropia

What is hypermetropia?

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.

Qu'est-ce qu'une erreur de réfraction ?

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).

Section transversale de l'œil

Refraction refers to the bending of light, in this case by the eye, in order to focus it. A refractive error means that the eye cannot focus light on to the retina properly. This usually occurs either due to abnormalities in the shape of the eyeball, or because age has affected the workings of the focusing parts of the eye.

Il existe quatre types d'erreurs de réfraction :

• Short-sightedness (myopia).

• Long-sightedness (hypermetropia).

• Age-related long sight (presbyopia).

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

Pour bien comprendre les erreurs de réfraction, il est utile de savoir comment nous voyons.

Sélection de patients pour Problèmes visuels

Santé des yeux

Qu'est-ce que l'astigmatisme ?

L'astigmatisme est une affection courante qui se corrige généralement facilement à l'aide de lunettes, de lentilles de contact ou, parfois, d'une intervention chirurgicale. Nous verrons ici ce que cela signifie pour vous et ce que vous pouvez faire pour y remédier.

par Simon Berry, MCOptom

Santé des yeux

Flotteurs, éclairs et halos dans les yeux

Eye floaters and flashes are common symptoms which often affect normal eyes. They usually occur because of changes that happen in the jelly-like substance inside the eye (which is called the vitreous humour). The most common causes need no treatment, do not prevent normal visual tasks and tend to settle by themselves. However, flashes and floaters can occasionally be warning signs of a serious condition, such as a retinal tear or retinal detachment. Haloes are bright circles which seem to surround a source of light. They are also referred to as glare. They are a common symptom, particularly in older people. They can be unpleasant and uncomfortable and lead to temporary dazzling; this may particularly affect driving at night. They can sometimes be a sign of underlying eye conditions such as glaucoma.

par le 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.

Mise au point de l'œil

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.

La cornée et le cristallin ont pour fonction de focaliser la lumière. La cornée fait le plus gros du travail, car elle courbe (réfracte) les rayons lumineux qui passent ensuite dans le cristallin, qui ajuste finement la mise au point. Pour ce faire, le cristallin modifie son épaisseur. C'est ce qu'on appelle l'accommodation. Le cristallin est élastique et peut devenir plus plat ou plus arrondi. Plus le cristallin est arrondi (convexe), plus les rayons lumineux peuvent être courbés vers l'intérieur.

La forme du cristallin est modifiée par de petits muscles du corps ciliaire. De minuscules structures ressemblant à des cordes, appelées ligaments suspenseurs, sont attachées d'un côté au cristallin et de l'autre au corps ciliaire. C'est un peu comme un trampoline dont la partie centrale serait le cristallin, les ligaments suspenseurs seraient les ressorts et les muscles ciliaires seraient le rebord.

Lorsque les muscles ciliaires du corps ciliaire se contractent, les ligaments suspenseurs se relâchent, ce qui fait grossir le cristallin. Cela se produit pour les objets proches. Pour regarder des objets éloignés, le muscle ciliaire se détend, les ligaments suspenseurs se resserrent et le cristallin s'amincit.

Une plus grande courbure (réfraction) des rayons lumineux est nécessaire pour faire la mise au point sur des objets proches, comme lors de la lecture. Une moindre courbure de la lumière est nécessaire pour faire la mise au point sur des objets éloignés.

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).

• Maux de tête.

• 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?

Lunettes

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.

Lentilles de contact

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).

Ils nécessitent cependant plus de soins et une hygiène méticuleuse, et ne doivent pas être portés pendant la baignade, la douche ou le sommeil. Ils conviennent mieux aux adolescents plus âgés et aux adultes qu'aux très jeunes enfants.

Chirurgie oculaire au laser

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.

La résolution complète et permanente de l'erreur de réfraction est possible chez un certain nombre de personnes. D'autres bénéficient d'une amélioration significative, même si la vision parfaite n'est pas atteinte et que des lunettes ou des lentilles de contact peuvent encore être nécessaires.

Ces problèmes s'améliorent généralement avec le temps. Une sur-correction ou une sous-correction de la myopie peut également se produire.

Les complications comprennent les infections oculaires et la sécheresse des yeux. La perte permanente de la vision est très rare ; si cela se produit, environ 1 personne sur 5 000 a besoin d'une greffe de cornée pour restaurer sa vision. Jusqu'à 1 patient sur 10 peut avoir besoin d'une intervention chirurgicale supplémentaire pour obtenir le meilleur résultat.

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

Chirurgie du cristallin

Échange de lentilles réfractives (ELR)

• 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.

• Les effets secondaires comprennent une gêne oculaire, des effets visuels (tels qu'une vision floue, des halos autour des lumières et des arcs d'ombre ou de miroitement autour des bords de la vision) et des hémorragies sous-conjonctivales. Ces effets s'atténuent généralement avec le temps.

• 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.

À quelle fréquence dois-je passer un examen de la vue ?

Le NHS recommande à la plupart des gens de faire contrôler leur vue tous les deux ans. Les enfants se verront systématiquement proposer des contrôles de la vue à différents stades, de la naissance à l'âge scolaire.

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:

• Le diabète.

• Augmentation de la pression dans l'œil (glaucome).

• Dégénérescence maculaire.

• Or a family history of these conditions.

Les personnes âgées de plus de 70 ans et les enfants qui portent des lunettes peuvent également avoir besoin d'examens oculaires plus fréquents.

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

Certains opticiens proposent un service de visite à domicile pour effectuer des tests de vue pour les personnes qui ne peuvent pas se déplacer.

Le Dr Mary Lowth est l'auteur ou l'auteur original de cette brochure.