Amblyopia, also called visual weakness, often manifests itself in early childhood and can have a variety of causes. Normally, the images that both eyes send to the brain are processed uniformly. This is one of the prerequisites for optimal vision.
In childhood, however, it sometimes happens that the brain prefers one eye because it provides a sharper image. The result: the brain neglects the images that come from the other eye and vision does not develop correctly. This problem is called vision weakness or amblyopia. The medical term for low vision is amblyopia, from the Greek for " dull or weak eye."
What is amblyopia?
An amblyopia is a visual impairment that occurs in childhood. People who suffer from it experience poor vision and therefore have limited visual perception.
In most cases, poor vision affects only one eye. However, both eyes can be affected. Typically, amblyopia occurs in children under the age of ten.
Early treatment is very important, since visual impairment that is not corrected in childhood can cause problems for the whole of adult life with respect to their visual capacity. Because the development of the eyes is completed between the tenth and twelfth year of life.
A large hyperopia not corrected in time can cause binocular amblyopia due to the fact that poor quality blurry images are formed in both retinas.
If a child is squinting or if there are signs of an eye disease, it is important that an ophthalmologist can evaluate it as soon as possible.
Even if a child has difficulty recognizing objects, it can indicate an eye sensitivity, such as having toys and things close to them to recognize them, or turning his head to the side when trying to focus his vision.
The amblyopia often not recognized immediately: this is because most of the time one eye is healthy and can compensate for the lack of vision of the other to some extent, because the healthy eye still can provide a good image to the brain.
However, this has the consequence that visual development takes place only in the healthy eye; thus, the eye affected by amblyopia is neglected.
Vision weakness is characterized by massive restrictions in acute vision, and contrast vision is also severely impaired. Typical signs are:
· Reading and writing problems.
· Difficulty with spatial vision.
· Perception of the disturbed contour.
· Blurry vision.
· Myopia or hyperopia.
What are your causes
An amblyopia arises when the brain obtains such different images of both eyes in the long term, that it cannot make them meet in a visual impression. The most common cause is strabismus.
When a child makes small turns with his head when trying to look, or looks forward with one eye while the other points up, down or to the side, he will perceive different images with each eyes. To avoid double vision, the brain often fades images from the poorer-looking eye and uses only one eye.
In about 60 to 70% of children with this strabismus condition, amblyopia develops, but only in 2% of children who do not have it.
Another common cause of amblyopia are so-called refractive errors. Which cause the image of the retina of an eye to be out of focus. There are three different types of refractive errors:
1. Myopia: the eye can only focus on close objects.
2. Hyperopia: the eye can only focus on objects in the distance.
3. Astigmatism: the eye perceives everything blurry because the lens or the cornea is deformed. Astigmatism is often spoken of.
Refractive errors are more likely to result in amblyopia if both eyes are affected differently: that is, if one eye has a refractive error and the other does not, or in the case of having myopia in one eye and presenting in the other farsightedness.
Poor vision is rarely triggered by eye disease. These include, for example, clouding of an ocular lens (cataract), a drooping eyelid (ptosis), corneal scar, exudate in the vitreous, complete covering of the eye after injury, or the absence of an ocular lens (aphakia).
What is its frequency?
Amblyopia is one of the most common causes of visual impairment in one or both eyes, and it is a common condition. Its incidence is estimated at 1-3% in healthy children and 4-5% in children with eye diseases. Most data indicate that approximately 2% of the general population has amblyopia.
How Amblyopia Is Diagnosed
A complete eye exam can determine the degree of amblyopia and its cause.
There are several studies that allow an ophthalmologist to determine if a child has amblyopia, and these are recommended to be performed early:
· With the help of eye charts, the doctor can determine how well the child can see. The eye test used depends, among other things, on the age of the child. For infants and young children there are special tests.
· Performing a physical exam helps identify other problems that can cause amblyopia, such as blurring of the lens.
· A slight squint is not always visible to the naked eye. To determine if the child has it, the position of his eyes can be determined, for example, with a test in which the eyes are covered one after another. The doctor then looks to see if the other eye is moving.
· In a so-called skiascopy, a beam of light is directed towards the eye with a special instrument (the skiascope) and how the retina reflects light is examined. By keeping different correction lenses in the light beam, the refractive power of the eyes can be accurately determined.
These tests are generally safe. Before a skiascopy, the eye drops are usually given to dilate the pupils. These agents can occasionally cause burning or irritation in the eyes.
Treatment of amblyopia
Treating amblyopia is a long and difficult process. It will also depend on several factors, including the cause of the eye condition.
Treatment of amblyopia in a child is established based on its cause, for example, complete correction of vision defects (refraction), followed by lazy eye exercise.
The most effective treatment method is occlusion of the eye with better visual acuity. However, it is not always possible. If the view is low or medium or high, the child will not be able to cover it.
In some cases, a slight deviation of the eyes from the correct position due to poor convergence (that is, difficulties with convergent movement of both eyeballs when looking closely) can be corrected with exercises of the muscles of the eyes. eyes These include sliding pencil exercises and computer vision therapy.
The younger the child is, the greater the plasticity of the brain and the greater the possibility of improving amblyopia. Starting treatment after age 7 may generally have less effect.
Unfortunately, the older the child, the more intensive the therapy parents require. In adults, we cannot apply corrective exercises to the wandering eye (strabismus), because the visual plasticity of the cortex disappears. Amblyopia for one eye is treated with surgery in adults, if possible, depending on the specific cause.
How to avoid amblyopia?
Well-child checkups for young children prevent amblyopia and help start their treatment early. It should be carried out in infancy, before the age of 7, and when the child's caregivers notice any disturbing symptoms.
The anticipated vision screening should be performed in children born prematurely whose refraction and strabismus are more common than in children born at term, and children whose family member has had any of the following vision conditions:
· refractive errors,
· congenital eye diseases.
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