Find out about sleep and why you get dry eyes at night

family sleeping in bed


It’s universally accepted that sleep is a necessary part of our routine and is essential to how we function. For many of us, the reasons behind why this is the case might be unclear. This article will explain what actually happens when we sleep, the effects that a lack of sleep can have on the body and particularly the eyes. We also look at the cause of “sleep in your eyes”, as well as tips for caring for your eyes before bed and in the morning.



Why do we need to go to sleep?

Many of us may consider sleep to be a period in which the body simply shuts down and rests for a few hours, but this is not the case. The truth is that sleep plays a far more important role in our day-to-day functioning than many of us give it credit for.

During sleep, the body actively carries out a lot of processing and restoration and plays an essential role in the consolidation of memories. It also significantly aids many bodily processes such as growing muscle, repairing tissue, replacing chemicals and synthesising hormones necessary for growth.

Sleep is essential to the body’s cognitive functioning. It has been shown that a continued lack of sufficient sleep has a detrimental impact on the part of the brain responsible for language, memory and planning. It is even claimed that 17 hours of sustained wakefulness can negatively impact an individual’s performance to an extent equivalent to that of drinking two glasses of wine.


What happens during sleep?

Over the course of the day, our brains take in massive amounts of information. So much so, it can’t all be immediately logged and recorded. Instead, this information first needs to be stored and processed. Much of this happens during sleep, where pieces of information are transferred from our short-term memory to our long-term memory in a process known as “consolidation”. Sleep also aids the immune system in fighting infection. A lack of sufficient sleep can leave the body more vulnerable to viruses that cause colds and flu.

Different activities occur during different phases of sleep. People can enter REM sleep within the first 90 minutes of falling asleep and as the sleep cycle repeats throughout the night, REM sleep can occur several times nightly. During this period the eyes will flutter from side to side, muscle tone will drop and dreams can be particularly vivid.

Non-REM sleep appears to be a more productive period of sleep. Brainwaves, breathing and heart rate slow down, providing respite, while the aforementioned consolidation and growth hormone release largely occurs in non-REM sleep. Thermoregulation also happens during non-REM sleep, where the body is able to optimise its temperature, even when the surrounding temperature is different.


How much sleep do we need?

Due to the importance of sleep with regards to retaining information and learning new skills, the amount required is very much dependent on age. Naturally, children who are constantly learning throughout the stages of their development, require significantly more sleep than adults.

Generally, adults are considered to require between seven and nine hours of sleep per night, while newborns and toddlers can log in up to 16 hours. As children reach primary school-age, they will need an average of 9-11 hours, while people over 65+ generally require around 7-8 hours per night.

Despite these general guidelines, there is no fixed amount of sleep for everybody within an age bracket, as it is largely dependent on the individual. You simply need enough sleep to refresh yourself and be able to function the following day.


What is insomnia?

Insomnia is the term reserved for difficulty with sleeping, be it trouble getting to sleep, staying asleep or having non-refreshing sleep. An insomniac will have such difficulties at least three times a week and it may persist for at least a month. Insomnia can impact work performance, cause low energy levels and could even lead to depression. However, as opposed to feeling sleepy during the day, sufferers can remain in an awakened state, feeling sluggish and somewhat lifeless.

Insomnia tends to be more prevalent amongst older people, who are generally lighter sleepers. Women also suffer from insomnia more than men, which is considered to be due to factors such as pregnancy and child rearing, hormones, periods and the menopause.

Anxiety and stress are frequent causes of insomnia. Other conditions such as depression, asthma and schizophrenia can also contribute to insomnia, as can certain medications and misuse of drugs or alcohol prevent the individual from falling asleep.


How does insomnia / lack of sleep affect our bodies and eyes?

The physical toll that insomnia can have on the body is pretty extensive:

  • Lack of sleep has also been linked to hunger and appetite. 
  • Low libidos and decreased interest in sex in men and women can be a consequence of insomnia, resulting from depleted energy and sleepiness.

It is recommended that the eye requires at least five hours of sleep each night to replenish and refresh itself with essential nutrients in order to work to its full potential. Lack of sleep or insomnia can lead to numerous side effects:

  • One of these is myokymia or involuntary spasms of the eyelid. Whilst not painful or damaging to your vision, these spasms can be rather aggravating.
  • Both eye strain and dry eye can also occur as a result of sleep deprivation.
  • Lack of sleep is also known to cause sallow skin and puffy eyes, whilst more severe lack of sleep can lead to a lack of skin vitality, fine lines and dark circles under the lines. This is caused by an excessive amount of cortisol, a stress hormone that the body releases when it is lacking in sleep. Cortisol is known to break down skin collagen, which is the protein that keeps skin smooth and vitalised.


What about rheum?

You may be more familiar with the term “sleep in your eyes”, than rheum, which is the term given to eye discharge that builds up in the corner of your eyes while you are sleeping. It consists of a combination of mucus, oil and skin cells.

Your eyes produce mucus throughout the day and the night, but during the day a continuous film of tears effectively washes your eyes when you blink, wiping out the rheum before it has a chance to accumulate. However, when you are sleeping, you are unable to blink and so eye discharge can build up in the corners of your eyes.

The eye can produce mucus in response to allergens in the air. Consequently, if allergens are around, you may experience more rheum. It is normal to wake up to find some discharge in your eyes. However, excessive amounts, along with other effects, such as light sensitivity or blurry vision, can be an indication of more serious eye conditions, in which case you should consider seeking advice from a healthcare professional.


Eye care before bed and in the morning

Prior to going to bed, it is important to avoid things that could impact your natural biological clock or have a negative effect on your eyes. The use of electronics that emit artificial light, shortly before bed, such as laptops and mobile phones, is something to avoid in particular, as this light can affect both your biological clock and your eyes.

The removal of contact lenses and make up is also advisable before bed, if not earlier. Contact lenses can block the flow of oxygen to the eyes and absorb fluids from its surface. Wearing contact lenses to bed could significantly increase your risk of suffering from dry eye and its associated effects.

Keeping eye make up on, such as mascara or eyeliner, for prolonged periods of time can increase the risk of eye contamination. 

To remove rheum when you wake up, a natural impulse might be to simply pick it out. However, it’s never a good idea to go near your eyes with your hands as it risks spreading germs. Dampening a clean washcloth in water and placing it over your eyes, before wiping away the discharge, can be an efficient and hygienic way of dealing with rheum.

Similarly, placing a warm compress over your eyes can help to relieve symptoms associated with eye strain and dry eye that may have been brought on by sleep deprivation. These include irritability and soreness. Also, regularly cleansing the eyes is a good way to maintain eye hygiene.


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