Amblyopia

Conditions Basics

What is amblyopia?

Amblyopia is a childhood problem that happens when one eye is weaker than the other. The brain chooses to take in images from the stronger eye and ignore images from the weaker eye. This means that your child uses the strong eye more than the weak eye. If the weak eye doesn't have to work, it isn't able to develop good vision. This leads to poor vision in the weaker eye.

Amblyopia usually affects only one eye.

The problem starts between birth and about age 7. Your child may not even know that they are using only one eye. Ignoring the images from the weak eye is an automatic response. Your child has no control over it.

Early treatment usually can reverse amblyopia. The younger your child is when treatment starts, the more likely your child is to have good vision.

Amblyopia is sometimes called "lazy eye."

What causes it?

Any condition that prevents your child's eyes from forming a clear, focused image or that prevents the normal use of one or both eyes can cause amblyopia. It may happen when:

• The eyes do not focus on the same object. This is called strabismus. When this happens, the brain chooses to receive the images from only one eye.
• Your child is much more nearsighted or farsighted in one eye than in the other. If one eye sees much more clearly than the other, the brain ignores the image from the weaker eye.
• A problem prevents light from entering the eye for a long period of time. A problem in the lens, such as a cataract, or in the clear "window" at the front of the eye (the cornea) may cause amblyopia.
• Someone else in your family had it or if your child had a premature birth or low birth weight.

What are the symptoms?

In most cases, amblyopia does not cause symptoms. But your child may:

• Have an eye that wanders or does not move with the other eye.
• Have eyes that do not move in the same direction or fix on the same point.
• Cry or complain when one eye is covered.
• Squint or tilt the head to look at something.
• Have an upper eyelid that droops.

How is it diagnosed?

Your child's doctor will do an eye exam. If the exam shows that your child has poor vision in one eye, the doctor may diagnose amblyopia after ruling out other causes.

To help make the diagnosis, the doctor will ask about symptoms, any family members who have had vision problems, other possible risk factors such as low birth weight, and whether your child has trouble reading, seeing the board in school, or watching TV.

The Canadian Paediatric Society recommends screening to detect lazy eye (amblyopia), misaligned eyes (strabismus), and defects in visual acuity in children younger than 5 years of age. ^{footnote 1} If you have concerns about your child's eyes or vision, call your child's doctor, or take your child to an eye doctor.

How is amblyopia treated?

For amblyopia to be treated, your child must use the weak eye. This will force the eye to get stronger. Over time this corrects the vision in the weak eye.

Your doctor may suggest:

• Blocking the strong eye with an eye patch.
• Blurring the strong eye with eyedrops or glasses.

Your child may have to wear the patch or glasses most of the day or for just part of each day. Treatment may last for a few weeks or months. Severe cases may take longer.

If another problem is causing the amblyopia, such as a cataract, it also needs to be treated.

Treatment is best started before age 6 and should begin before your child's vision has fully developed, around age 9 or 10.

After treatment ends, be sure to set up follow-up eye examinations for your child. Amblyopia can return even after successful treatment.

How can you help your child?

Treatment sounds simple, but using an eye patch or glasses may bother your child. To help your child:

• Explain that the glasses or patch will help his or her vision get better.
• Tell your child's friends, teachers, coaches, and others about the eye problem and what you and your child have to do for it. Ask for their help.
• Use the patch, glasses, or eyedrops as your doctor says.
• If possible, decorate the patch with your child. First, ask your doctor if it's okay.
• Do fun things, such as colouring and crafts, when your child is wearing the patch or glasses. This will help your child use the weak eye.