What is a Lazy Eye?



Everyone's heard the phrase or the term a lazy eye, but it's very difficult sometimes to understand what that actually means.  

A lazy eye is technically called an amblyopic eye. Now, very simply, an amblyopic eye is an eye that doesn't see as well as the other one does, even when corrected with glasses. So with glasses on, people assume that both eyes are going to be able to be corrected to the same level, so that each eye should see the same with glasses on, but that's not always the case. For example, if one eye can be corrected with glasses to read the very bottom line of the chart, the other eye might only be able to read halfway down the chart. Now that eye is the lazy eye, the amblyopic eye. And no matter what you do in terms of glasses, it's never going to come down to the same level as the other eye. So, that is what we term a lazy eye. 

Now, there are a couple of reasons why this happens and the hard bit to get your head round is that it happens because it's your brain protecting you. Sounds a weird thing to say that your brain is protecting you by giving you a lazy eye. But the eye itself, a lot of the time when we look in their eye, it quite shocks them sometimes to be told that their eye is clear, healthy, and perfectly normal, but they don't understand why it doesn't work. "Well, why can't I see out of the eye if the eye is perfectly healthy and normal?" Because, it's the brain. We see with our brain.  

So what's happening? 

Okay, couple of reasons why you might get a lazy eye. The first one is the eyes aren't lined up. So, say one eye's pointing straight ahead, the other eye, it's pointing in. Now if you allow both eyes to see, and both eyes to have an input to your brain, you're going to see two of everything because they're not pointing at the same thing. So your brain is protecting you and allowing you to be able to function normally by shutting off the message from one eye and that's why we developed this lazy eye. It doesn't develop the ability to see as well because the brain shuts the message off. It's just closing that message off and allowing you to see with the one good eye. 

It's very clever. It's an evolutionary thing. You couldn't hunt wooly mammoth if you saw two wooly mammoths every time there was one, you miss it every time if you were throwing spears at them or whatever cave people did. Okay, so I'm not that great at that sort of pre-history sort of stuff, I have to admit. But yeah, it's evolutionary so you can survive better by not seeing everything as double. 

The other thing, the other common reason for getting a lazy eye, if one of your eyes when you're very young needs very, very, very strong glasses compared to the other eye. Your brain again knows that one eye sees clearly, but the other eye, it's all blurred. If your brain tries to put those two pictures together, a lovely clear image and an incredibly blurred image, it's going to mess up the clear image. It's going to blur the good image that you're getting. So again, it's a form of protection. It protects you from having poor eyesight and it actually enables you to see better by shutting off the message to the brain. So again, the eye does not develop clear vision because it's just basically turned off. 

So again, these are perfectly normal, healthy looking eyes when you look inside them, but the brain has very cleverly protected you from either poor vision or double vision by switching them off. Which is why one of the main treatments in childhood for a lazy eye or amblyopic eye, is to actually put a patch over the good eye to get the eye to switch on and the brain to trigger that eye and actually use that eye to develop some good vision. And then later on in life you find that if that's worked well, then you sometimes we get equal vision in each eye, which is phenomenal, or just a very mild, lazy eye. So you might get a lazy eye that's only maybe one or two lines behind the other eye on the chart, as opposed to only being able to see the very top letter or no letters at all on the chart. 

So that gives you some idea of why we get a lazy eye, what it actually is, and what it means. It's an amblyopic eye so it doesn't see as well as the other eye does when corrected. That's the main thing because you might just be shortsighted a bit more in one eye than the other and think "I must have a lazy eye because I can't see as well across the room with my right eye compared to my left eye." But actually put glasses on and both eyes see the same, so that's not a lazy eye. A lazy eye is, even with glasses on, one eye sees better than the other and it's incredibly common. Our brain is so powerful, it's a way of protecting us and allowing us to function normally and lead more of a normal life rather than seeing everything blurred or everything double. 

I hope that helps a bit. I can do another video about the reasons why eyes turn, because there's a few different reasons and how that's corrected. It's not always a surgical route, sometimes it's just glasses, but that's a bit too much to add to this piece now!


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