lazy eye

lazy eye

"Contrary to what some believe, a lazy eye is not one that doesn't like to wake up and go to work in the morning."

- Anonymous Eye Doctor with a sense of humour

The medical term for Lazy Eye is Amblyopia

So why do eyes become lazy?

  • The brain is very picky! When it is not receiving a clear image or if it is receiving double images, it begins to shut off connections to the eye that is causing it the most grief
  • This process usually happens during childhood and if it is caught before the age of 7, it can be reversed depending on how bad the situation is and how cooperative the patient is

There are two main situations in which this happens:

  • Eye turn
    • In this case, the patient probably has double vision so the brain will stop communicating with the eye that is turned in/out, which will stop the double vision
    • Sometimes surgery is needed to straighten the turned eye, other times simple wearing a patch over the good eye will help force the turned eye back
  • Difference in prescription
    • If there is a large difference and one eye is very blurry, the brain will again shut it off because it doesn't like dealing with two eyes producing different images
    • Glasses are the obvious answer. Sometimes a patch over the good eye will help force the blurry eye to work harder

As you can see a Lazy Eye problem actually becomes more of a Picky Brain problem.

And as the saying goes, "you can't teach an old dog new tricks".

So, once the brain has made all the connections it wants to make, it is very difficult to make it go back. This is why it is important to catch it early! (Before age 7 or 8)

After this cutoff, even providing a patient their full prescription may not improve their vision because no matter how clear the image is, it is not being sent to the brain.



Q: Can a person have 2 lazy eyes?

A: That is a fantastic question! And, yes. I recently blogged about a patient I had seen who had high astigmatism in both eyes. So the connections for both eyes were not fully formed during childhood due to blurry vision and at this point in her life, glasses did not help very much.

Q: What is astigmatism?

A: The answer to this can be found in am earlier post called "All Kinds of Blurry" along with info on other causes of blurry vision

Q: How early should kids have their eyes checked?

A: Both the Canadian and American Association of Optometrists recommend that children have their first eye exam at 6-12 months and again at age 3.

Why don't my glasses help?

Last week, I had a patient (let's call her Mary) come to see me because she noticed that she was having difficulty seeing the board at the front of the class clearly. Mary was in her early 30s and mentioned she had worn glasses for a little while as a teen but never thought they helped very much.

Turns out that our friend Mary has a prescription with high astigmatism in both eyes. While many of my near-sighted friends and patients can attest that their vision progressively gets worse throughout their teenage years and into their twenties, astigmatism is generally present from childhood and remains relatively constant throughout our lives. (Learn more about astigmatism in the "All Kinds of Blurry" post)

Why is this important? This means that since Mary was a child, her brain has been receiving blurry images. And our mushy, emotion-filled noodle is a very picky person. If it sees blurry images (or double images, for that matter), it will stop forming connections with the eye that it dislikes (in Mary's case, that was both of her eyes!).

This process is called Amblyopia. If we catch these types of high prescriptions before the age of 7, its usually simple enough to reverse the process and convince our gray and white-mattered friend to start liking the patient's eyes again. Unfortunately, in a case like Mary's there is not too much to be done. At this point, not glasses or contacts, not even lasers will be able to significantly improve her vision.

But this doesn't mean we don't try! A lower prescription was given that did mildly improve vision and we hope that Mary's eyes (and brain) will adapt with time.

What is the moral of the story? Kids should get their eyes examined early and often to catch high prescriptions or changes in prescriptions and to avoid amblyopia!