What is nocturnal lagophthalmos?
Nocturnal lagophthalmos, sometimes referred to as nighttime lagophthalmos, is a condition where the eyelids do not fully close during sleep. In some cases, this may leave the eyes completely open. Other people may sleep with their eyes half open or just slightly open.
Lagophthalmos (la-guhp-THAL-mowz) is the general medical term for when the eyelids do not close completely. If this happens while you’re awake, it can be easier to diagnose than the nocturnal variant. This is especially so if your eyelids close normally during the day but not when you’re sleeping.
It can be hard to detect signs or symptoms of this condition since it occurs while you’re asleep. While your eyes may be open, the brain activity responsible for making sense of visual data is still temporarily off during sleep. As a result, it’s hard to know if this is happening unless someone observes you.
Additionally, even though lids may appear to be closed during a doctor’s examination, this doesn’t mean they’re fully sealed. And if the lids aren’t properly sealed, it means they aren’t protecting the eyes from drying out overnight.
Estimates of sleeping with the eyes open vary significantly. 5% of adults and up to 20% of the overall population are reported to experience nocturnal lagophthalmos. These estimates also vary according to ethnicity.
Statistics specifically for children have not been reported. However, some babies do sleep with their eyes partially open. Cases of children sleeping with their eyes half open when they're sick have been reported, but this finding is uncommon.
Because of the nature of nocturnal lagophthalmos, it is very likely underdiagnosed.
LEARN MORE: What your eyes do while you’re asleep
Symptoms & causes
Sleeping with your eyes open is usually linked to an underlying cause, such as nerve or muscle damage. It’s important to determine how regularly symptoms are happening and if they started alongside or following another condition.
Signs and symptoms
The biggest sign of nocturnal lagophthalmos is the eyes opening while sleeping. If you’re unsure whether this is happening, other signs and symptoms may be easier to recognize. These include:
- Red, irritated or dry eyes
- Sensitivity to light
- The sensation of having something “stuck” in your eye
- Blurred vision
- Development of a sore (ulcer) on the cornea
- Watery eyes
These symptoms will typically be worse upon waking and may get better throughout the day. Many of these symptoms overlap with dry eye disease and may be exacerbated in people who already have this disorder.
Causes
Sleeping with your eyes open doesn't always mean there's a serious problem. It may also happen in otherwise healthy individuals. But lagophthalmos, nocturnal or otherwise, can occur alongside other conditions or factors. These can include:
- Exophthalmos/proptosis – Bulging eyes (such as in Graves’ disease)
- Conditions that affect the eyelid – Such as ptosis (droopy eyelid), lid deformities or ectropion (outward turning of the eyelid), especially in seniors
- Neuromuscular conditions – Such as amyotrophic lateral sclerosis or Kearns-Sayre syndrome
- Cosmetic procedures – Such as Botox or blepharoplasty (eyelid surgery)
- Facial paralysis – Conditions affecting the seventh cranial nerve, like Bell’s Palsy
- Nerve damage – Caused by eye injuries, stroke, tumors, infections, autoimmune disorders or congenital conditions like Moebius syndrome
Excessive alcohol intake and sleep medications have also been linked to sleeping with your eyelids open.
While this condition is likely related to an identifiable pre-existing condition or event, there are also cases of idiopathic nocturnal lagophthalmos, meaning the cause is undetermined.
Risks of sleeping with your eyes open
Closed eyelids help protect the front of the eye during sleep, helping to maintain the tear film — the thin layer of liquid that protects and lubricates the front surface of the eye (the cornea). If the tear film is exposed for long periods of time, it can dry out, meaning it can’t do its job correctly.
Nocturnal lagophthalmos leaves the eyes partially or fully exposed overnight, potentially leading to disruptions in the tear film. This not only causes discomfort but erodes the eye’s ability to protect itself. These disruptions can lead to conditions like xerophthalmia and keratopathies, which can eventually progress to vision loss.
It could also affect your quality of sleep. In addition to protecting the eye from drying and irritation overnight, eyelids help block out light and visual input to the cerebral cortex. Light transmitted through closed eyelids can already contribute to circadian sleep disorders. It is suggested that open eyes during sleep may worsen this effect.
LEARN MORE: Parts of the eyelid and how they work
Diagnosis
Diagnosis of nocturnal lagophthalmos can be tricky because it occurs during sleep. Additionally, your eyelids may appear to fully close when you’re awake, or they may close enough that it seems like they are adequately sealed when they are not.
Observation alone might not be enough to deliver a definitive diagnosis. In these situations, an eye doctor will likely use the Korb-Blackie light test. This test involves shining a transilluminator light just above the eye, over the upper tarsal plate. If light leaks onto the cheek, it indicates the eyelid is not sealing correctly.
A recent study explored the capabilities of artificial intelligence for diagnosing lagophthalmos. The software correctly classified still images of lagophthalmos patients about 93% of the time. While this technology is in its early phases, such software may greatly simplify diagnosis in the future.
Treatment
It’s important to treat this condition early to prevent damage to the eye and tear film over time. There are several simple, noninvasive ways to help keep your eyelids closed at night, such as:
- Using eyelid tape (applied over the eyelid from the cheek to the forehead, pulling up the cheek skin to keep the eye closed)
- Using eyelid weights (a tiny metal weight, usually gold, taped to the eyelid)
- Wearing fabric or moisture-preserving sleep masks
- Improving your sleep hygiene
- Adjusting sleep medication or alcohol intake
Nocturnal lagophthalmos treatment should also address the effects on the eye. Many symptoms can be improved with treatments that preserve moisture in the eyes, such as:
- Oil gland treatment
- Eye drops, gels or ointments
- Warm compresses
- A humidifier to counteract a dry environment
- Moisture-chamber goggles
Treatment for any coexisting or relevant condition may also help improve symptoms.
If conservative strategies do not help the eyelids seal or adequately treat symptoms, surgical options may be recommended. Surgical procedures may vary but can involve:
- Modifying the upper eyelid muscles
- Implanting weights in the eyelids
- Expanding or tightening the eyelids
Animals who sleep with one eye open
The term lagophthalmos originates from lagos, the Greek word for “hare.” At one point, hares were believed to sleep with their eyes open. This is now generally not believed to be true, although there are animals that can sleep with one or both eyes open. These include:
- Cetaceans, like whales, dolphins and porpoises
- Northern fur seals
- Migratory birds, like mallard ducks and great frigate birds
- Draughtsboard sharks
In many cases, the animal’s physiology allows one hemisphere of the brain to remain active while the other sleeps. Keeping one or both eyes open during sleep helps some animals avoid predators. For others, like aquatic animals, it allows them to maintain their breathing and body temperature.
When to see an eye doctor
To prevent any long-term effects from nocturnal lagophthalmos, it’s important to consult an eye doctor early on. If your eyes are dry or watery, you have the persistent feeling of something stuck in your eye or you experience changes in your vision, contact your eye doctor to schedule an eye exam.
Some symptoms of nocturnal lagophthalmos and dry eye disease overlap. There is also evidence of the two conditions being related. If you’re already seeking treatment for dry eye disease, consider whether nocturnal lagophthalmos could be a contributing factor. Asking a partner or friend to observe whether your eyes are open while you sleep at night could be helpful.
If this is not possible, keep track of whether your symptoms are worse in the morning, regardless of whether they resolve during the day.
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