What is it about ?
The light rays enter the eye through the pupil.
Through a phenomenon called “refraction,” the cornea deflects rays to focus or form the image on the lens, which in turn forms it on the retina.
The lens is responsible for the accuracy of the image. Its role is to make it possible to distinguish the details. To allow us to see distant or near objects without having to make any effort, the lens can become distorted; this phenomenon is called “accommodation”. Accommodation is provided by muscles inside the eye that act on the lens.
If the refraction is abnormal, the eye is no longer able to properly deflect the light rays. The image of objects is then not formed on the retina. Most refractive errors start in childhood and can then get worse, but sometimes get better.
The most common refractive errors are hyperopia, myopia, presbyopia and astigmatism.
Hyperopia
The eye is too short, or the refractive power is too low. The rays then form the image behind the retina, for both near and far objects. When the person is young, he still manages to correct the image by unconsciously contracting the muscles of the eyes. With age, this deformation of the lens becomes more and more difficult, and the person can no longer see well up close, although he can see far objects well.
Certain eye abnormalities are more common in farsighted people.
Myopia
The eyeball is too long, or the refractive power is too strong. In this case, the rays form the image of distant objects in front of the retina. The person can see well up close, but cannot see distant objects.
Retinal detachment is more common in nearsighted people.
Presbyopia
With age, the lens becomes much less flexible and therefore adapts less well. Presbyopia sets in from the age of 40.
Astigmatism
The eyeball is oval in shape instead of round. The refraction of light is good in one direction, but not in another. Astigmatism is usually associated with myopia or hyperopia.
What is their frequency?
Refraction disorders are observed in 7 out of 10 Belgians. Those affected do not always consult a general practitioner; many people go directly to the ophthalmologist. One in three young adults is nearsighted.
Babies are usually always farsighted when they are born. As they grow older, the eye axis lengthens, so that by the age of 3 to 4 years the child has (almost) no refractive abnormalities. If the eye grows too much, the child becomes myopic. This often occurs at the age of 6 to 12 years.
How to recognize them?
Refractive errors are responsible for a decrease in the ability to see image details (visual acuity) for near or far objects. Sometimes they also cause more vague symptoms such as fatigue, headache, pain around the eyes, burning sensation in the eyes, or eye strain.
With myopia, the person cannot see distant objects, while people with good eyesight can distinguish them well. Short-sighted people sometimes have to squint to watch TV. On the other hand, they have no problem reading a book.
In case of hyperopia, the person should hold the book away from them in order to be able to read it, while they have no problem distinguishing distant objects.
How is the diagnosis made?
Usually, the GP will send you to an ophthalmologist to determine which refractive error you have.
What can you do ?
Usually there is nothing you can do about refractive error on your own.
What can the doctor do?
In order for incoming light rays to form the image on the retina, they must be properly refracted. To correct the problem, you can wear glasses or suitable contact lenses or undergo laser treatment or have the lens replaced with an artificial lens. The general practitioner will refer you to an optician or an ophthalmologist.
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