What do your eyeballs do when you fall asleep?

Falling asleep is a mysterious process that scientists are still working to fully understand. One of the most noticeable changes that occurs when we fall asleep is that our eyes close and our eyeballs go through a series of movements. In this article, we’ll explore what exactly happens to our eyes when we drift off to sleep.

Table of Contents

Why Do Our Eyes Close When We Fall Asleep?

Closing our eyes when we sleep seems like a pretty basic thing, but there’s actually a complex physiological process behind it. Here’s a quick overview of what’s happening:

As we begin to fall asleep, the reticular activating system (RAS) in the brainstem starts to slow down. The RAS helps keep us awake and attentive during the day.
With the RAS dampening its excitatory signals, the frontal and parietal lobes of the brain become less active. These areas are involved in functions like reasoning, attention, and integration of sensory information.
The reduced input from the RAS and higher brain areas allows the sleep promoting centers, like the ventrolateral preoptic nucleus (VLPO), to kick into action.

The VLPO inhibits the neurotransmitters involved in wakefulness and works to reduce muscle tone throughout the body.
One of the muscles relaxed by the VLPO is the levator palpebrae superioris, which controls the opening of the eyelids.
With this muscle relaxed, the eyelids naturally close due to their own weight.

So in summary, the shutting of our eyes when we sleep is due to active relaxation of the muscles controlling eyelid elevation as areas like the VLPO promote sleep and inhibit wakefulness. It’s not just a passive result of the body falling unconscious.

Do Your Eyes Roll Back When You Sleep?

As the eyelids close and the eyeballs roll back, only the whites of the eyes are visible from the outside. But what’s really happening behind those closed lids? Here’s a look at how eye positioning changes with sleep:

When we are awake and alert, our eyes are oriented forward in a natural, straight-ahead gaze.

As we begin to fall asleep, the extraocular muscles (the muscles controlling eye movement) start to relax.
This relaxation allows the eyes to drift to an upward facing position.
The upward roll of the eyes is called Bell’s phenomenon, named after the Scottish anatomist who first described it in 1836.

Bell’s phenomenon helps protect the eyes by pulling them out of the way of possible damage when the lids are closed.

So in most cases, the eyes do roll back as we fall asleep. However, the degree of eye roll varies between individuals. Some people may only show a slight upward drift, while others exhibit a more dramatic Bell’s phenomenon with the eyes pointing far upwards under closed lids.

What Happens During REM Sleep?

One of the most active eye movement phases of sleep is REM (rapid eye movement) sleep. Here’s an overview of how our eyes behave during this stage:

REM sleep occurs about 90 minutes after we first fall asleep and then cycles every 90 minutes throughout the night.
During REM, the eyes dart back and forth quickly under closed eyelids.
These REMs give this sleep stage its name and can be easily observed by watching a sleeping person’s eyelids.

The bursts of REM are controlled by nerve signals from an area at the base of the brain called the pons.
REM sleep is associated with vivid dreaming, since brain activity kicks up a notch relative to other sleep stages.
The reason for REM is still unclear. Some theories suggest it may be involved in memory consolidation or stimulation for the developing brain.

So in summary, REM sleep is where we see the most eye movement during sleep. The rapid darting may relate to activities occurring in the brain during dreaming.

Do Your Eyes Move in Non-REM Sleep?

In addition to REM sleep, we cycle through stages 1-3 of non-REM (NREM) sleep. So what are eyes doing during these stages? Here’s an overview:

Stage 1 NREM is the transition between wakefulness and sleep. Eyes move slowly or roll as we begin to disengage from the waking world.

Stage 2 NREM is identified by bursts of rapid eye movements along with sleep spindles and K-complexes seen on EEG readings.
Stage 3 NREM is known as slow wave or deep sleep. The eyes are still during this restorative phase.
Overall eye movement is much slower and more sporadic in NREM compared to REM.

However, people may briefly open their eyes during NREM sleep. This is more common in the lighter stages and rarely occurs during deep NREM.

So in summary, the eyes continue to demonstrate some level of movement and activity during NREM sleep, though not nearly as vigorously as REM. Brief opening of the eyes can also occur.

What About Eye Twitching?

Many people report experiences with eye twitching or fluttering under their eyelids when trying to sleep. What’s behind this phenomenon?

These involuntary muscle spasms are known as myokymia.
Eye twitching results from spontaneous firing of the nerves controlling the orbicularis oculi muscle around the eye.
It’s often triggered by fatigue or stress, which can overwhelm the nerves and cause them to misfire.

Eye twitching tends to happen as we are falling asleep, rather than in deep sleep stages.
These spasms are harmless, though annoying, and often resolve with rest and relaxation.

So in summary, eye twitching results from overexcited facial nerves triggering the muscles around the eyes. Letting yourself unwind may help reduce this sleep-interfering phenomenon.

Why Can You Sometimes See Behind Closed Lids?

Some people report being able to faintly see objects in the room even when their eyes are closed at night. What explains this phenomenon?

Even with eyelids shut, a small amount of light still reaches the retinas through the skin of the lids.
When we are awake with eyes closed, visual signals get suppressed by the brain so we don’t continuously perceive an image.

During early and light sleep stages, this suppression may become imperfect, allowing some visual information to leak through.
The effect is usually brief and most pronounced right at the transitions between waking and sleep.
Some types of hallucinations can also involve seeing imagery with eyes closed while falling asleep or upon waking up.

So in summary, glimpses behind closed lids likely represent a failure to completely block retinal signals as sleep sets in. The ability tends to fade during deeper sleep stages.

What About Eyes Opening During Sleep?

While our eyelids remain shut for most of the night, they sometimes flutter open briefly during sleep. What’s behind this phenomenon?

Brief eye opening typically occurs during lighter sleep stages or transitional phases.

Muscle tone loss is incomplete during these stages, allowing the lids to briefly drift open.
The eyes then automatically close again due to an innate protective reflex.
Episodes last just a few seconds and don’t disturb the overall sleep structure.

Some medications and substances like alcohol can increase the chances of eyes opening during sleep.

So in summary, brief openings of the eyes during sleep are harmless events that result from incomplete muscle relaxation in lighter sleep. The eyes reflexively shut again to maintain the integrity of the sleeping state.

What Happens if You Sleep With Eyes Partially Open?

Rarely, some people have a condition that causes them to sleep with their eyes at least partially open. What are the implications of this unusual sleep phenomenon?

Sleeping with eyes open is called nocturnal lagophthalmos.
It results from impaired function of the facial nerve that controls eyelid closure.
Those affected tend to sleep with their eyes open only by a slit, not fully wide.

Potential risks include dry eyes, light sensitivity, and even damage to the corneas.
Treatments aim to lubricate and protect the eyes and tape them closed at night as needed.
Addressing underlying causes like facial paralysis may help in some cases.

So in summary, sleeping with eyelids open is an uncommon condition that requires treatment to prevent complications to eye health from excessive dryness and light exposure during the vulnerabilities of sleep.

Why Do Eyes Move Erratically Before Waking?

Right before we wake up in the morning, our eyes often move erratically back and forth beneath our lids. What causes this pre-awakening eye activity?

These quick eye movements are our brains warming up the oculomotor regions as we prepare to open our eyes and engage visual attention.

They help take the eyes “offline” after a night of rest and back “online” for visually-driven waking consciousness.
The timing helps ensure eyes are oriented properly for integrating visual data upon eyelid opening.
Pre-awakening eye movements may also relate to the dissipation of REM sleep and its associated eye darting.

These actions help transition the visual system from the offline, internally-directed gaze of sleep to online waking perception.

So in summary, the quick eye rolls we experience before waking serve to prime the oculomotor system and visual cortex for the focused gaze and visual attention that accompanies conscious wakefulness.

Can You Control Your Eyes During Sleep Paralysis?

Sleep paralysis occurs when you wake up before REM sleep has finished. You remain unable to move despite waking awareness. Can you control your eye movements in this state?

During sleep paralysis, the mechanism that paralyzes muscles during REM to prevent acting out dreams is still active.
The eye muscles are unaffected by this mechanism, unlike limbs and most other voluntary muscles.
So while the body remains immobilized, the eyes usually regain full voluntary control.

Being able to move the eyes helps signal to the brain that waking consciousness has returned.
Many report using intentional eye movements as “panic buttons” to try to wake themselves from sleep paralysis episodes.

So in summary, while limbs remain immobilized in sleep paralysis, the unique oculomotor system is spared from paralysis. This allows eyes to be moved intentionally, which can be leveraged to try to break free from the episode.

Conclusion

Our eyes go on quite a journey each night during sleep. From gently closing as sleepiness sets in, to the darting motions of REM, to the final warm up as we transition back to wakefulness, our ocular system is anything but at rest overnight. Understanding these eye behaviors provides a window into the hidden workings of the sleeping brain. Paying attention to our eyes can reveal a lot about what’s going on beyond our conscious awareness during sleep. The next time you drift off, think about what your eyeballs are up to behind those closed lids as you travel through the cycling landscapes of sleep.