Eyelids provide protection for the surface of the eye, the cornea. Blinking replenishes the normal tear film and removes debris on the corneal surface. During sleep the eyelids provide important protection from air and debris that can irritate or damage the cornea.
Nocturnal lagophthalmos occurs when the lids remain partially open during sleep. It is more common in those with thyroid disease, prior eyelid surgery, or with a CPAP machine for sleep apnea. Symptoms include dryness and irritation that is usually worse in the morning. If untreated this condition can lead to corneal scarring affecting vision.
Treatment includes lubricating eye drops with ointment applied before bed and sleeping masks. Occasionally the condition is severe enough to warrant eyelid surgery. Long term prognosis for patients with lagophthalmos is good, provided treatment is initiated early and administered regularly.