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What actually happens to your eyes when you sleep?

Monday, November 30, 2015 @ 05:11 PM
Author: Amit Mathur

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Do you ever wonder why you see what you see when you dream? Though nothing is known for certain, there are speculations as to what happens to our eyes when we sleep and dream.

Certain things are known. For one thing, when you close your eyes, your eyes are still able to detect light. This is why we sleep better in the dark, why when the sun rises or when someone turns on the light we are woken up. Our eyelids protect our eyes from the external visual cues that might otherwise keep us awake. Also, our eyelids keep our eyes from drying out over the night by keeping the moisture to the cornea. This is a very important part of what happens.

When you’re awake, your eyes send information constantly and at such a rapid-fire rate to your brain, you don’t even notice it’s happening. However, when you are sleeping, your eyes stop sending your brain this “visual data” so the response and processing times slow down naturally. This is why when you do wake up, it takes your eyes a little bit of time to readjust to what you’re seeing and the light. It can take up to 30 seconds for your eyes and your brain to wake up.

You may have heard of the different stages of sleep. There are altogether five stages: 1, 2, 3, 4 (called non-REM) and the fifth stage, REM (rapid eye movement). Generally speaking, you go through each of the five sleep cycles repeatedly when you sleep, but not equal amounts of time are spent during each of the stages.

  • 30% is spent during stages 1, 3 and 4

  • 50% is spent during stage 2

  • 20% is spent during REM

So what happens during each stage of sleep?

Stage 1: your eyes roll slowly sometimes opening and closing a little bit.

Stages 2-4: your eyes are completely still and you fall into a deeper sleep.

REM: your eyes start to move around in all directions really fast. Despite your eyes not sending any information to your brain, the part of your brain that processes this visual information (called the visual cortex) is still found to be active during REM. Scientists believe that this is happening because your brain is, in essence, storing all the visual information you received during the day. And as it turns out, this is the time when you dream.

A study at Tel Aviv University found that our eyes function the same during REM sleep and when we are awake and sending image information to our brain for processing. This same research concluded that our eyes are in fact responsible for the images we see in our dreams and the neurons in our brain continue to react the same when we are dreaming. That is to say, the images you see while you are dreaming are images you’ve already processed when you were awake, only this time your brain is telling your eyes what it wants to see.

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