Ophthalmology – Exposure Keratopathy

Exposure keratopathy is corneal damage caused by excessive evaporation of the tear film and abnormal tear distribution when the eyelids do not close or blink properly. Inadequate eyelid protection leaves part of the cornea exposed, resulting initially in epithelial breakdown and, in severe cases, corneal ulceration, infection, thinning, scarring, or perforation.

Exposure keratopathy is relatively uncommon overall, although its prevalence increases with age and in hospitalized or neurologically impaired patients. Prevention depends on identifying patients at risk and protecting the ocular surface before significant corneal damage develops. This is particularly important in patients undergoing general anesthesia or intensive care, where incomplete eyelid closure and reduced blinking can rapidly cause exposure-related injury.

Pathophysiology

Normal blinking continuously redistributes the tear film across the cornea. The tear film contains aqueous, lipid, and mucin components, all of which contribute to maintaining a smooth, hydrated, and protected ocular surface.

When eyelid movement is reduced or the lids cannot close completely, several abnormalities develop. Tears evaporate excessively from the exposed portion of the cornea, fresh tears are not adequately spread across the ocular surface, and normal mixing of tear-film components is impaired. Tear drainage and recycling through the nasolacrimal system may also become abnormal.

The result is progressive desiccation of the corneal epithelium, followed by punctate epithelial erosions and potentially more severe epithelial breakdown.

Etiology

Exposure keratopathy has several important causes. Neurogenic causes include facial nerve palsy, particularly Bell palsy, where weakness of the orbicularis oculi prevents complete eyelid closure.

Anatomic causes include cicatricial eyelid disease, previous blepharoplasty, Stevens–Johnson syndrome, other mucocutaneous scarring disorders, eyelid malposition, and proptosis from conditions such as thyroid eye disease or orbital tumors.

Degenerative neurologic disorders such as Parkinson disease, Alzheimer disease, and advanced dementia may decrease spontaneous blink frequency and contribute to exposure.

Patients with an altered level of consciousness, including sedated, critically ill, or anesthetized patients, are also at increased risk because spontaneous blinking and voluntary eyelid closure are reduced or absent.

Common associated conditions include Bell palsy, lower eyelid ectropion, Parkinson disease, and neurotrophic corneal disease.

Diagnosis

The history often reveals an underlying condition associated with impaired eyelid closure or blinking. Patients may report that their eyes remain partially open during sleep, known as nocturnal lagophthalmos.

Symptoms typically develop subacutely or chronically and may include foreign-body sensation, photophobia, excessive tearing, irritation, and decreased visual acuity.

An important exception occurs in patients with associated neurotrophic keratopathy. Because corneal sensation is reduced, these patients may have advanced epithelial damage with surprisingly little pain or discomfort.

Physical Examination

External examination should assess spontaneous blinking and eyelid closure. Findings may include lagophthalmos, reduced blink frequency, a widened palpebral fissure, ectropion, eyelid retraction, or other eyelid abnormalities. Patients with facial nerve palsy may also demonstrate brow ptosis and weakness of facial movement.

The patient should first be observed blinking spontaneously. They should then be asked to gently close the eyes and subsequently close them forcefully. Any residual opening between the eyelids should be measured.

Corneal sensation should be tested before topical anesthetic is applied, particularly when neurotrophic disease is suspected.

Slit-lamp examination frequently demonstrates punctate epithelial erosions, typically most pronounced in the inferior cornea, corresponding to the exposed portion of the ocular surface. In more severe exposure or markedly reduced blinking, epithelial abnormalities may become diffuse.

Other findings may include decreased tear breakup time and reduced tear production, particularly in patients with facial nerve dysfunction. Severe or prolonged disease may progress to persistent epithelial defects, corneal ulceration, microbial infection, stromal thinning, scarring, or perforation.

Fluorescein staining helps demonstrate the extent of epithelial damage and can be used to evaluate tear-film breakup. A Schirmer test may be helpful when associated aqueous tear deficiency is suspected.

Assessment of Bell phenomenon can be performed, but its clinical value is limited because the position of the eye during voluntary examination does not always accurately predict globe position during sleep.

Differential Diagnosis

Important differential diagnoses include dry eye syndrome, Sjögren syndrome, neurotrophic keratopathy, medication-related ocular surface toxicity, and blepharitis.

Exposure keratopathy and neurotrophic keratopathy can coexist. This combination is particularly dangerous because the eye experiences both mechanical exposure and impaired epithelial healing, while reduced corneal sensation may delay recognition of severe disease.

Treatment

The first objective is to maintain continuous lubrication and protection of the exposed cornea.

Artificial tears may be used frequently during the day. More viscous gels provide longer-lasting lubrication, while ophthalmic ointments provide the longest protection and are particularly useful at bedtime.

Treatment intensity should correspond to the severity of exposure. Mild nocturnal lagophthalmos may require only nighttime ointment, whereas marked facial nerve palsy with a wide palpebral opening may require very frequent lubrication throughout the day.

Eyelid taping during sleep can help maintain closure. In hospitalized, sedated, or unconscious patients, the eyelids may be taped closed or covered with an appropriate transparent moisture-retaining dressing to prevent corneal drying.

Additional Therapy

Moisture chambers or moisture goggles reduce evaporation and can be very effective, especially during sleep.

Punctal occlusion can help retain tears in selected patients.

Soft bandage contact lenses have a limited role because reduced blinking and impaired ocular surface defense may increase the risk of infection. When used, they require careful ophthalmologic monitoring.

Scleral lenses can be particularly useful in selected chronic cases because they create a reservoir of fluid over the cornea, protecting the epithelium while providing a stable optical surface.

Patients who have both exposure and neurotrophic corneal disease should generally be managed with a corneal specialist because of their substantial risk of sight-threatening complications.

Surgical Treatment

Surgery should be considered when lubrication and conservative measures are inadequate or when the underlying eyelid abnormality is unlikely to resolve.

Patients with ectropion or horizontal eyelid laxity may require eyelid tightening procedures, such as a lateral tarsal strip.

In facial nerve palsy, placement of a weight in the upper eyelid can improve passive eyelid closure by gravity. Lower eyelid elevation or tightening may also be necessary.

Patients with upper eyelid retraction may benefit from recession of the eyelid retractors. If proptosis is responsible, treatment may include orbital decompression or removal of an orbital lesion, depending on the cause.

A partial or complete tarsorrhaphy may be required in severe or persistent cases. This procedure partially closes the eyelids to reduce the amount of exposed cornea.

Botulinum toxin can occasionally be injected into the upper eyelid elevator muscles to create a temporary protective ptosis, although its onset is delayed and the amount of corneal coverage can be variable.

Follow-up

Patients with acute or worsening exposure keratopathy require close ophthalmologic follow-up, particularly when an epithelial defect is present.

Monitoring should focus on the extent of epithelial breakdown, corneal thinning, signs of infection, visual acuity, eyelid closure, and progression or recovery of the underlying disease.

Patient Education

Patients should understand the importance of regular lubrication and complete eyelid protection, particularly during sleep.

They should seek urgent ophthalmologic assessment if they develop sudden worsening of vision, increasing pain, photophobia, redness, or discharge, because these findings may indicate corneal ulceration or infection.

Prognosis

The prognosis depends on the severity, duration, and underlying cause. Mild exposure treated promptly generally resolves without permanent damage.

Longstanding or severe exposure, particularly when accompanied by neurotrophic disease, carries a substantially greater risk of permanent visual impairment.

Complications

The major complications are persistent corneal epithelial defects, corneal ulceration, microbial keratitis, stromal thinning, corneal scarring, and corneal perforation. Severe untreated exposure keratopathy can therefore become a sight-threatening condition.