Amblyopia

What is amblyopia?

Vision is not mature at birth; it develops in the first years of life. The brain will gradually learn to “see” during this period.

The two eyes are in competition throughout the development of vision. If during the first years of life, the brain receives images of different quality from each eye, it will favour learning vision by using the best quality images, and will neglect “learning to see” with the worse eye. If the cause of the alteration in the quality of the images is not corrected in childhood, the abnormal visual development will cause permanent 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.
• A squint, which causes only one eye to fixate on the object of interest, because the other eye is not aligned. The brain will then ignore the images transmitted by the deviated eye.
• Much more rarely, an anatomical abnormality that prevents the formation of an image on the retina (for example, an eyelid that covers the eye (ptosis), corneal opacity, or a cataract).

What are signs of amblyopia in children?

Even if they have eyesight problems, children rarely complain about their vision. And this also applies to amblyopia, where children develop better vision in one of the two eyes.

If it is of refractive origin, amblyopia can go completely unnoticed, with the child adapting to living with only one functional eye. It is only when the good eye is hidden, during a game or a medical examination, that the poor vision of the other eye can be detected. Strabismus, eyelid abnormalities or abnormalities of the front of the eye may be visible, and are thus a warning sign of probable asymmetry of vision.

How can amblyopia be screened for in children?

Early visual screening is essential. In very young children, we look for an asymmetric reaction when one eye is occluded. If the child does not react when one of the eyes is hidden, but cries when the other is hidden, 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 must 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 the ocular anatomy.

What are treatments for amblyopia?

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.
• Make the image clear: correct, if necessary, a refractive disorder (hyperopia, astigmatism, myopia), with glasses or contact lenses
• Forcing the brain to use the “weak” eye: most often by covering the “good” eye with a patch 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 occlusion therapy (patch wearing) 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. Vision will then be checked after 4 to 6 weeks. Depending on the improvement obtained through wearing glasses, the ophthalmologist may decide to continue monitoring the evolution of your child’s vision, or start occlusion therapy.

How do I get my child to agree to wear his glasses?

Glasses change how children perceive images. To help them get used to wearing glasses, we recommend that they wear them as soon as they wake up. The child will therefore immediately see images corrected by their glasses, without having to get used to the transition from unaided vision to corrected sight. We also recommend that the child wears their glasses continually throughout the day. Furthermore, the glasses should have large enough lenses to cover all directions of the gaze, a nose bridge, and comfortable temples that ensure good stability.

How many hours a day will my child have to wear a patch?

The numbers of hours your child will need to wear the patch depends on their age and the extent of difference in vision between the two eyes, and can vary from one hour to continual wearing throughout the day. The time spent wearing a patch will be adjusted according to visual recovery during treatment.

During which activities should my child wear the patch?

Your child should wear their patch during activities that stimulate vision, such as near-sight games, reading books, or watching the television or other screens (not for too long, and not too closely, of course;-). Of course, it is not necessary for them to wear a patch during naps.

Depending on the length of treatment, the patch may sometimes need to be worn at school. We therefore recommend explaining the situation and its consequences to their 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.

How long will my child have to wear the patch?

Treatment should ideally be continued until symmetrical vision is achieved, and/or alternating fixation in the case of strabismus (i.e. the child squints sometimes with one eye, sometimes with 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 for treating amblyopia?

In some cases, particularly in the presence of significant hyperopia, we may consider “penalising” the image of the good eye with an 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 developing vision from the weaker eye. Beyond a certain age, the situation becomes irreversible, and the weak eye’s poor vision can no longer be improved.

Living with only one functional eye is perfectly possible. But if the good eye is damaged or “lost” due to illness or an accident, the situation can become very serious. It is mainly to avoid this risk that the treatment of amblyopia is essential.

What are the risk factors?

The presence of eye problems in the family, such as the wearing of glasses with a significant correction, strabismus, cataracts or glaucoma in the child, represents a slightly higher risk for children to also have a visual disorder. Some problems that occur during pregnancy or premature birth can 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.

Find out more about children's visual disorders

Do you want to learn more about a particular visual condition? Discover our pages on dry eye, nystagmus, conjunctivitis, and diplopia. We explain these visual disorders and tell you how to treat them to preserve your children’s visual acuity.