What your eyes do when you sleep

As you settle into bed after a long day you can feel your muscles and mind relax, but while they're relaxing what on earth are your eyes doing as you sleep? 

Once your eyelids close your eyes are shielded from the light to help you fall asleep. Even as your eyelids are closed your eyes are still functioning with the ability to sense light--this is why you may be awakened to a light being switched on or the sun rising.  

As you sleep your eyes take a break from sending visual information to your brain, but meanwhile are busy with a new task--rapid eye movement (REM).  

During sleep our bodies go through several different phases of sleep. The first phase is called Non-REM sleep, this phase is made up of stages 1, 2, 3, and 4. Your body progresses from stage 1 to 4 then goes into REM sleep and then the cycle restarts. Most of our total sleep (almost 50%) is spent in stage two, 20% is spent in REM sleep, and the rest (30%) is in the other stages.  

Now that we've laid the foundation with the phases of sleep, onto the question at large. What do your eyes do as you sleep? 

Stage 1 - Your eyes roll slowly and may open and close slightly.  

Stages 2-4 - Your sleep has become deeper and your eyes become still.  

Rapid eye movement (REM) - If the name didn't give it away already your eyes are moving around quickly in a range of directions. Before you panic remember, your eyelids are closed, so it's not as *ahem* creepy as it may sound.  

As your eyes are rapidly moving during REM sleep the part of your brain responsible for processing visual data (the visual cortex) is active and hustling. While you're catching Z's your brain is busy consolidating your memories. Fun fact, during REM your eyes are moving angular speeds of 900 degrees per second--that's the fastest movement produced by the human body!  

Some people, about 2%, experience REM sleep behavior disorder. Instead of experiencing the typical temporary stillness of your arms and legs during REM sleep an individual will act out their dreams. The onset of this disorder is usually gradual and worsens with time.  

Symptoms of REM sleep behavior disorder can include:  

• Talking, shouting, laughing, or crying during sleep.  
• Punching, sitting up in bed, flailing or jumping out of bed.  
• Being able to recall a dream if you wake during an episode.  

If you are experiencing any of the above symptoms or other sleep problems talk to your doctor.  

There you have it--what your eyes do as you sleep! Now enjoy the related article, 'How do eyes see at night?'