Eyelid & Exposure Conditions

Your eyelids are part of the tear system. Every complete blink helps spread tears across the ocular surface, distribute meibum and restore the tear film. When your eyes are closed, particularly during sleep, the eyelids also create a physical barrier that protects the cornea from the surrounding environment. If the eyelids do not close or align properly, an area of the ocular surface may remain exposed.

That exposed area can lose water more rapidly and become increasingly vulnerable to irritation and surface damage.

Why Blinking Matters

Exposure simply means that part of the ocular surface remains uncovered when it would normally be protected by the eyelids. Exposure can be:

• •brief or persistent
• •mild or severe
• •present while awake
• •or occur primarily during sleep

The cause can also vary. Some people cannot completely close their eyelids. Others have an eyelid that sits in an abnormal position. In some cases, the anatomy of the eye itself increases the amount of exposed ocular surface.

The important concept is the same: the tear film and ocular surface are being asked to remain stable in an area that is insufficiently protected.

Lagophthalmos means incomplete or defective closure of the eyelids. When the eyelids do not meet completely, part of the cornea remains exposed. TFOS DEWS III specifically describes lagophthalmos as incomplete or defective eyelid closure resulting in corneal exposure. It can occur for many reasons, including abnormalities of eyelid anatomy or position, facial nerve dysfunction, trauma, previous surgery and other conditions.

Sometimes eyelid closure appears normal during the day but is incomplete during sleep. This is called nocturnal lagophthalmos. And it can be particularly confusing because you usually cannot observe your own eyelids while you are asleep. A person may therefore wake up repeatedly with:

• •dryness
• •burning
• •redness
• •foreign-body sensation
• •eye discomfort

without realizing that part of the ocular surface may have remained exposed overnight. TFOS DEWS III specifically recognizes exposure from intermittent lagophthalmos, including nocturnal lagophthalmos, as a potential contributor to dry eye disease.

No. This is important. Morning symptoms can occur for many reasons.

Having dry, red or uncomfortable eyes when you wake up does not prove that you have nocturnal lagophthalmos. Likewise, someone telling you:

“Your symptoms are worse in the morning, so you must sleep with your eyes open.”

is making a conclusion that the symptom alone cannot support. Morning symptoms are a clue. Eyelid closure and the ocular surface still need to be examined.

No. We discussed this distinction earlier, but it is worth repeating.

Incomplete blinking means that the eyelids do not fully close during a spontaneous blink.

Lagophthalmos means that the eyelids do not completely close when they should remain closed, for example during deliberate closure or sleep.

A person can have incomplete blinks but still close the eyes completely during sleep. Another person may blink relatively normally while having incomplete closure at night. They are related eyelid problems, but they are not the same finding.

When exposure begins to damage the corneal surface, the term exposure keratopathy may be used. The exposed corneal epithelium can become dry and disrupted. Depending on severity, clinicians may see:

• •punctate corneal staining
• •epithelial damage
• •and, in more serious cases, persistent epithelial defects or other corneal complications

This is why significant exposure is more than simply a comfort issue. The eyelids are part of the cornea’s protective system.

Yes. The eyelids need not only to close, they also need to sit properly against the eye. Two examples are:

Ectropion

The eyelid, usually the lower lid, turns outward or sits away from the eye. This can interfere with normal tear distribution and leave part of the ocular surface inadequately protected.

Entropion

The eyelid turns inward. This can cause the eyelashes or eyelid skin to rub against the ocular surface, creating mechanical irritation and damage.

TFOS DEWS III includes ectropion and entropion among anatomical abnormalities relevant to identifying dry-eye etiological drivers. So although both are eyelid-position abnormalities, they affect the ocular surface in different ways.

Yes. If the eyes project farther forward than usual, a larger area of ocular surface may remain exposed and complete eyelid closure may become more difficult. One important example is thyroid eye disease, in which proptosis and upper-eyelid retraction can substantially increase exposure in some patients. TFOS DEWS III discusses treatment of severe exposure associated with thyroid eye disease and lid retraction. We will discuss thyroid disease separately in the systemic-conditions section because the relationship between thyroid disorders and dry eye is broader than exposure alone.

Thyroid Disease and Dry Eye

Yes. The facial nerve helps control the muscles responsible for eyelid closure.

Facial nerve palsy can therefore interfere with the ability to close the eye completely, resulting in persistent lagophthalmos and corneal exposure. TFOS DEWS III specifically uses facial nerve palsy as an example of a condition that can produce constant lagophthalmos. In these cases, protecting the ocular surface can become particularly important because the mechanical problem may be substantial.

Yes. Certain surgeries around the eyelids or face can alter eyelid position or closure. Scarring, tissue changes or changes in eyelid tension can occasionally result in:

• •retraction
• •malposition
• •incomplete closure

This is another reason why a history of previous eye, eyelid or facial surgery matters during a dry-eye evaluation.

Dry Eye After Eye Surgery

It can, depending on where and how it is used. Botulinum toxin weakens targeted muscles. If the orbicularis oculi, the muscle involved in eyelid closure, is affected, blinking can become weaker and lagophthalmos or eyelid malposition can occur. TFOS DEWS III discusses poor blinking, lagophthalmos and ectropion as possible mechanisms by which periocular botulinum toxin treatment can contribute to corneal dryness.

That does not mean Botox inevitably causes dry eye. It means altered eyelid mechanics are one possible adverse effect and one potential explanation to consider when symptoms develop after periocular treatment.

Imagine a tear film covering the cornea. Normally, blinking regularly redistributes that film. Then the eyelids close during sleep and protect the surface for hours. Now imagine that one small area remains uncovered.

That area is exposed to the surrounding air for much longer. Water can evaporate from the tear film, the film can destabilize, and the epithelial surface underneath can become stressed or damaged.

So in exposure-related dry eye, the central problem may not initially be “I don’t make enough tears.” It may instead be “My tears cannot adequately protect an area that remains exposed.”

That distinction matters because it points toward a very different driver.

The Tear Film: how a healthy tear film works

It can. Ocular-surface staining may sometimes be concentrated in the region that remains exposed. The location and pattern of staining can therefore provide useful clues. But staining by itself does not prove exposure.

Many ocular-surface conditions cause staining. As with the other diagnostic tests in this guide, the finding has to make sense together with eyelid anatomy, closure, blinking, symptoms and history.

A clinician can examine:

• •eyelid position
• •the relationship between the eyelids and the globe
• •blink completeness
• •voluntary eyelid closure
• •the amount of visible ocular surface
• •the pattern of corneal and conjunctival staining

If nocturnal lagophthalmos is suspected, the history may also be useful. The key is not simply to ask “Are your eyes dry in the morning?” It is to look for evidence that the eyelids are actually failing to protect part of the ocular surface.

How Dry Eye Is Diagnosed

Yes. Severe lagophthalmos can be obvious. Subtle exposure may not be. A very small gap between the eyelids, partial blinking or intermittent nocturnal exposure can be much less apparent during a routine daytime examination.

This is another example of why dry-eye diagnosis sometimes requires looking beyond tear-production numbers and gland images. The eyelids themselves need to be assessed.

Treatment depends heavily on why the exposure is happening and how severe it is.

Management may involve strategies that improve lubrication and protect the ocular surface as well as treatment directed at the underlying eyelid or anatomical problem. For persistent or severe lagophthalmos, TFOS DEWS III discusses surgical options such as eyelid weights, lid reconstruction and partial or complete tarsorrhaphy. But this does not mean everyone with mild nocturnal exposure needs surgery. Treatment should match the underlying mechanism and severity.

We will discuss specific treatment options later in the treatment chapter.

Treating Dry Eye: Start with the Target

Not necessarily. Exposure may be the dominant driver in one person and only one contributor in another. Someone can simultaneously have:

• •MGD
• •aqueous deficiency
• •ocular-surface inflammation
• •abnormal blinking
• •exposure

Correcting the exposure can remove an important source of stress from the ocular surface. But it does not automatically correct every other dry-eye driver.

Dry Eye Is Often Mixed