What is amblyopia?
Vision is not mature at birth, but develops during the first few years of life. The brain will gradually learn to “see” during this time.
The two eyes compete with each other throughout the development of vision. If during the first years of life, the brain receives images of different quality from each eye, it will focus on learning to see using the best quality images, and will neglect “learning to see” with the weaker eye. If the cause of the deterioration in image quality is not corrected in childhood, the abnormal visual development will cause permanently poor vision in one or both eyes.
Amblyopia can be caused by:
- a refractive disorder (hyperopia, astigmatism, myopia), responsible for a blurred image. It is the most common cause of amblyopia.
- strabismus, which causes one eye to stare at the object of interest because the other eye is out of alignment. The brain will then ignore the images transmitted by the deviated eye.
- much more rarely, an anatomical abnormality that prevents an image from forming on the retina (for example an eyelid that covers the eye (ptosis), corneal opacity, or cataracts).
What are the signs?
Even if they cannot see well, children rarely complain about a problem with their sight.
If it is refractive in origin, amblyopia may go completely unnoticed as the child adjusts to living with only one functional eye. It is only when the good eye is covered, during play or a medical examination, that poor vision in the other eye can be detected. Strabismus, an abnormality of the eyelids or the anterior part of the eye may be visible and therefore constitute a warning sign of a probable vision asymmetry.
What are the means of screening for amblyopia?
Early visual screening is essential. In toddlers, we will try to observe an asymmetric reaction when one eye is covered. If the child does not react when one eye is covered, but cries when the other is covered, a difference in vision should be suspected.
In older children, it becomes possible to test the visual acuity of each eye, looking for a difference between the two eyes.
If poor vision is suspected, additional examinations should be carried out by the ophthalmologist to find the cause. The ophthalmologist, who often works with an orthoptist, examines refraction, looks for strabismus and examines eye anatomy.
What are the treatments ?
Treatment of amblyopia has three components:
- Offering vision to the eye: operating on an eyelid that completely covers the eye or removing opacity from the eye’s transparent media (cornea, lens, vitreous body), such as a cataract.
- Making the image clear: correcting a refractive disorder (hyperopia, astigmatism, myopia, etc.), if necessary, with glasses or contact lenses
- Forcing the brain to use the “weak” eye: most often by covering the “better” eye with a patch for a few hours a day.
The earlier the treatment is carried out, the more effective it is. After a certain age, it is no longer possible to re-train the brain to “see” with both eyes. Early detection is therefore essential.
At what age should treatment by occlusion (wearing a patch) be started?
The earlier amblyopia treatment is started, the faster and more effective it is. Treatment should therefore be started as soon as the visual problem is identified. At first, glasses will be prescribed if necessary. The vision is then checked after 4 to 6 weeks. Depending on the improvement obtained by wearing the glasses, the ophthalmologist may choose to continue to monitor the evolution of vision, or to start occlusion treatment.
How do I get my child to agree to wear glasses?
Glasses change the images seen by the child. To help them get used to the glasses, it is recommended that they wear them when they wake up. Children will therefore immediately see the corrected image with their glasses, without having to get used to the transition from the image perceived without glasses to the corrected image. It is also recommended that children constantly wear their glasses during the day. In addition, the glasses must have lenses large enough to cover the different directions of gaze, a nose bridge and comfortable temples that ensure good stability.
How many hours per day will my child have to wear a patch?
The number of hours to wear the patch depends on the child’s age and the size of the difference in vision between the two eyes, and can vary from one hour to all day. The duration of the occlusion is adjusted based on visual recovery during treatment.
During which activities should my child wear the patch?
Children should wear their patch during activities that stimulate vision, such as near vision games, reading a book, in front of the television or another screen (not too long, not too close of course; – ). It is of course unnecessary to wear the patch during naps.
Depending on the length of treatment, the patch may need to be worn at school. It is then recommended to explain the situation and its issues to the teacher, who can discuss it in class.
What if my child refuses to wear the patch?
Although children’s acceptance of the patch varies greatly, in the vast majority of cases it is accepted without too much difficulty. Children who refuse to wear the patch at the start of treatment, or who keep taking it off, usually get used to this over time. Decorated patches (pirates, princesses, etc.) often help the child to better accept wearing them. The more time passes, the more the “weak” eye’s vision will improve, making occlusion of the good eye easier to bear. It is, of course, essential that parents stick to the treatment, as they are the ones who will need to carry this out at home. Parents’ patience and perseverance is essential for successful treatment. Today, decorated patches (pirates, princesses, etc.) can often help children to better accept wearing them.
How long will my child have to wear the patch?
Treatment should ideally be continued until symmetrical vision is obtained, and/or a change of fixation in the case of strabismus (that is to say, if it is noted that the child sometimes squints one eye, and sometimes the other). The duration of treatment therefore depends on individual development, which differs for each child. Treatment usually lasts from a few months to a few years. The earlier the treatment is started, the faster and more effective it is.
Are there alternatives to the patch?
In certain cases, and particularly when this concerns significant hyperopia, we may “disadvantage” vision in the good eye with Atropine eye drops. Atropine prevents the good eye from focusing (accommodation), creating blurred vision which will encourage the brain to use images from the “weak” eye.
What happens if amblyopia is not treated?
The brain will continue to neglect learning to see with the weaker eye. <<<<<< Beyond one year old, the situation becomes irreversible, and the poor vision of the weak eye can no longer be improved.
Living with only one functional eye is quite possible. But if the good eye is “lost” due to illness or accident, the situation can turn dire. It is mainly to avoid this risk that treatment for amblyopia is essential.
What are the risk factors ?
The presence of eye problems in the family, such as wearing glasses with a major correction, strabismus, cataracts or glaucoma in the child, represents a slightly higher risk for children to also present a visual disturbance. Some problems that occur during pregnancy or premature birth also pose a risk. If in doubt, it is important to discuss the situation with your paediatrician and do not hesitate to consult an ophthalmologist.