Amblyopia

Amblyopia, also known as "lazy eye", is one of the most common causes of vision loss in children. Despite how common amblyopia is, many parents can find it a difficult condition to understand. There are many misconceptions surrounding what causes it, whether it can be treated, and how to treat it, so let's learn more about amblyopia here!

What is amblyopia?

Amblyopia is technically a problem with how the brain learns to see.

Babies are not born with 20/20 vision. Our ability to see the world develops rapidly in early childhood and most scholars would agree that development of the "vision part" (the visual cortex) of our brain slows down or even stops by the time we are between 7-10 years of age.

The brain learns to see objects in our world by getting the images of these objects from the eyes. This constant input from the eyes strengthens the connection between the eyes and the brain. The brain also learns to combine the images from both eyes to make a 3D image of the object in front of us.

Now, let's say the brain is only getting a blurry image from one eye. The brain then only learns to see blurry from that one eye. If only one eye sees blurry and the other eye sees clear, sometimes the brain may even shut off getting images from the blurry eye because it is too difficult to combine the images from the blurry eye and the clear eye. This weakens the connection between the brain and the blurry eye, and the blurry eye may then get even weaker.

Since development of the visual cortex of our brain only occurs in early childhood, amblyopia needs to be treated early (i.e. while the visual cortex of the brain is still developing). Otherwise, a child could end up with permanent vision loss if the brain never learns to see properly through the blurry eye.

Picture A shows the normal connections between the eyes and the vision part of our brain. Picture B is an example of how amblyopia develops. This picture shows what happens when one eye sees blurry. The brain shuts off receiving images from this blurry eye, weakening the connection between this eye and the brain over time. Picture C shows how patching can be used to treat amblyopia. By placing an eye patch over the stronger eye, the brain must learn to see through the blurry eye. This strengthens the connection between this eye and the brain.

What causes amblyopia and how do you treat it?

Here are some common causes of amblyopia :

• Refractive error (refractive amblyopia): 
  • Refractive error refers to how the shape of the eye affects how light enters the eye. 
  • Examples of refractive error include nearsightedness (myopia), farsightedness (hyperopia), and astigmatism. Too much of any of these can cause blurry vision. 
  • If there is a large difference in refractive error between the two eyes, the brain ignores the eye with the greater refractive error because this is the eye that is blurrier. 
  • Usually glasses are used to correct refractive error. Patching of the good eye is also often done to promote use of the weaker eye and strengthen the connection between the weaker eye and the brain.
• Eye misalignment (strabismic amblyopia) : 
  • If the eyes are crossing in or drifting out, the brain ignores the image from one eye to prevent seeing double vision. 
  • Treatment for this type of amblyopia may involve a combination of glasses, patching, and possibly surgery to correct the misalignment.
• Something preventing visual input into the eye (deprivation amblyopia): 
  • This could be from a number of causes, such as a droopy eyelid, a tumor, a cataract, or an opacification on the surface of the eye. 
  • Depending on the cause, surgery may be required. Glasses and patching may also be part of the treatment plan.

What are signs that a child may have amblyopia?

• A child may may turn his/her head so that the better seeing eye is closer to an object. 
• A child may develop eye misalignment (crossing in or drifting out of the eyes). 
• A child may start to keep one eye shut or squint one eye more than the other. 
• A child may have a cloudy spot on the eye that you can see. 
• In most instances, it is really hard to know if a child has amblyopia. Often, nothing looks wrong with the child and amblyopia is only detected during a vision screen at school or at the pediatrician's office.

A child with a white spot on the eye, misalignment of the eyes, or an abnormal head position (such as a face turn) should see an eye doctor.

My child was just diagnosed with amblyopia. How many hours a day should my child patch and how long do I need to patch for?

This depends on how much difference in vision there is between the two eyes. Your child's eye provider will decide how much patching to do and for how long. Sometimes patching may be required until your child reaches a certain age. While studies have shown that there can be improvements in vision with patching even in children up to 14 years of age, patching is thought to generally not be as effective after a child has reached between 7-10 years of age.

My child was just diagnosed with amblyopia and hates the patching. Is it really necessary?

There is a possibility of permanent vision loss if amblyopia is not treated early and properly. Patching can be challenging at the start, but remember that the long term goal is to give your child the best shot at seeing well for the rest of his/her life. Glasses, laser, and surgery will not fix this type of vision loss down the road.

Often, parents find it hard to start patching because the child, in effect, must see the world through a blurry eye while the stronger eye is patched. As the weaker eye gets stronger and the connection between the brain and weaker eye gets stronger, patching becomes easier.

Here are some tips that may make it easier to patch:

• Family, friends, babysitters, caregivers, and teachers can ALL be involved with patching! The more adult figures in a child's life who provide positive reinforcement for patching, the more likely the child will become accepting of it. It is helpful if teachers are aware of a child's patching treatment and schedule. Teachers can help explain the child's situation to their classmates and encourage the student to complete his/her schoolwork as usual.
• You can show what patching looks like on a doll or stuffed animal to teach him/her about patching.
• You can add extra tape to reinforce a patch to make if harder to pull off. Some parents have found mittens and tube socks helpful as well.
• If patching is unsuccessful after much sustained effort, an eye drop that dilates the stronger eye to promote use of the weaker eye could be used. Note, how useful this eye drop can be will depend on the difference in vision between the eyes and the child's refractive error. The decision to use this eye drop can be made in conjunction with your child's eye provider.

Modeling patching on a stuffed animal or toy can help a child feel more at ease with his/her own patching.

My child is developing a rash from using the patch. What should I do?

You can switch eye patch brands. You can try cutting the patch into different shapes or placing the patch on in reverse position so the adhesive comes in contact with a different part of the skin. You can make sure you do not leave the patch on overnight so the skin has time to heal.

Cloth patches to put over glasses is an alternative if the above suggestions do not help. Generally this is not a first option because many children will still try to use their good eye by peeking around the cloth patch.

If your child develops a severe allergy to the eye patch, a dilating eye drop may be a good alternative.

Is there anything else I can do while patching to help my child's vision improve?

Keep your child visually engaged while the patch is on. A sleeping child with a patch on is not helping his/her brain learn to see with the weaker eye. Studies have not shown a significant difference between distance vision activities and near vision activities, although some eye doctors believe there is more brain stimulation if a child is engaged in near vision activities (e.g.: doing homework, coloring, working on an art project, playing a board game, using a screen up close).

Some final thoughts...

Remember, the end goal of amblyopia treatment is to get the blurry eye stronger so that the brain can see more clearly with this eye. Although most children will be able to see a substantial improvement in their vision with treatment, not every child will improve to 20/20 vision. In some cases, treatment for amblyopia may not succeed in improving vision and the decision of when to stop patching should be made together with your child's eye provider.

Note, the above information about amblyopia is for educational purposes only. If you are concerned that your child has amblyopia, please ask for a referral from your pediatrician or go see your local eye doctor for a formal eye evaluation.