In this particular episode of Ask an Eye Doc, you will learn:

  • What is a refraction
  • What is refractive error
  • How a high glasses prescription can lead to lazy eye
  • How to tell if your infant or small child needs a prescription for glasses

This is the third episode in a series about lazy eye. This episode will make more sense if you’ve already listened to:

  • episode 32 – What is lazy eye? Part 1: amblyopia defined
  • episode 33 – What is lazy eye? Part 2: strabismic amblyopia
  • episode 14 – What is farsightedness (hyperopia)?
  • episode 13 – What is nearsightedness (myopia)?
  • episode 1 – What is astigmatism?

Be sure to check out the next episode for more information about lazy eye:

  • episode 35 – What is lazy eye? Part 4: deprivation amblyopia
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If you have another question about lazy eye or any other eye-related condition, go to to be featured on Ask an Eye Doc!

For you readers out there, here’s the answer in written form:

In part 1 of this series, we learned how amblyopia, or lazy eye, is actually a brain problem and not an eye problem. We also talked about the three amblyogenic risk factors or eye conditions that can lead to amblyopia.

If that doesn’t sound familiar, be sure to listen to episode 32 first so that this episode makes more sense. Today’s episode focuses on the second amblyogenic risk factor I mentioned in episode 32, which is refractive error.

Refractive amblyopia

Refractive error is a just a fancy term for the strength of your prescription. It comes from the word refraction, which is the process used to figure out how strong your prescription is (you know… one or two?). Refractive amblyopia, therefore, is lazy eye caused by having a strong prescription.

Refractive amblyopia can be caused by high hyperopia, high myopia, or high astigmatism. If you don’t know what these terms are, be sure to check out episodes 14, 13 and 1 to learn about those types of prescription.

Refractive amblyopia can be unilateral, meaning it only affects one eye, or it can be bilateral, meaning it affects both eyes, depending on which eye has the high prescription.

If a baby is born with a strong prescription, he or she will develop refractive amblyopia unless he or she is prescribed a pair of glasses. The longer the child goes without glasses, the worse the outcome will be. If you wait too long before getting the first pair of glasses, the child may never see 20/20 out of the affected eye, even if given the correct prescription as an adult, which goes back to the definition of lazy eye from episode 32.

My 3-year-old patient

I saw a 3-year-old patient several weeks ago whose mother brought him in because he seemed to have poor depth perception and was running into things a lot.

After dilating his pupils and performing retinoscopy, which is a type of refraction where I shine light off the back of his eyes, I was able to determine that each of his eyes was very hyperopic, or farsighted. The best he could see with the new glasses prescription was 20/40 in each eye, which is twice as bad as standard vision. (Check out episode 29 to learn more about what 20/40 and 20/20 mean). This is because he has spent the first three years of life with blurred vision and his eye-brain connection has not yet been able to develop properly. His diagnosis: high hyperopia and bilateral amblyopia.

A couple weeks after the first visit, I was pleased to hear back from his mother that her son loves wearing his new glasses — he won’t take them off! His depth perception is much better, and he isn’t running into things anymore. As long as he continues to wear his prescription full-time, which it sounds like won’t be a problem, his vision with the glasses will get better.

He is scheduled to come back in 6 months for a follow-up visit. At that visit, I don’t expect that his prescription will change, but I do expect that his visual acuity will be better. I’m hopeful that we will be able to reverse his amblyopia completely.

Now you know!

So now you know what refractive amblyopia is!

If you have an infant or a small child that hasn’t seen an eye doctor yet, and especially if you notice some depth perception or vision issues, make sure you schedule an appointment with your local optometrist to have his or her eyes tested.



If you found this episode to be helpful, be sure to leave a 5-star review on iTunes by going to or you can support the show at
If you have another question about lazy eye or any other eye-related condition, go to to be featured on Ask an Eye Doc.
AAED 34: What is lazy eye? Part 3: refractive amblyopia
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