It is easy to believe that during the night, when our eyes are closed, the surface of our eyes are most protected from symptoms of dryness and irritation. For many people, this is not the case. In fact, some underlying conditions mean that nighttime can be the most damaging time for the eye’s front surface. If you find yourself waking up throughout the night with severe symptoms of dryness and irritation, or if you notice that your symptoms are particularly bothersome immediately upon awakening, you may be affected by some form of nighttime dryness.
The Main Cause of Nighttime Dryness
The most significant risk factor for increased nighttime dryness is a condition known as nocturnal lagophthalmos. Nocturnal lagophthalmos affects eyelid closure during sleep. In this condition, the eyelids may never fully shut, or may slowly drift open throughout the night, leaving a portion of the corneal surface exposed for long periods of time. This exposure leaves the cornea malnourished, and can cause disruption to the most superficial layer of the cornea. Severity of lagophthalmos can vary, meaning the area of damaged corneal surface can range from a millimeter to over half of the eye.
Nocturnal lagophthalmos can usually be identified during a routine eye exam, as it creates a distinguishable pattern of corneal irritation on the lower part of the eye. If this is the case and nocturnal lagophthalmos is contributing to your symptoms of dryness and irritation, your optometrist may recommend a series of gel eye drops or overnight ointments to use each night in order to keep the front surface of the eye protected. The use of an eye mask may also be effective in keeping the eyelids completely closed and helping to nourish the corneal surface during sleep.
Sleep Apnea and Dry Eyes at Night?
Few people know that sleep apnea can carry an increased risk for dry eye disease, particularly nighttime dryness, due to several sleep factors. Those who have been diagnosed with sleep apnea may be treated with a prescribed medical device known as a CPAP machine. A CPAP (continuous positive airway pressure) device is a mask that fits over the mouth and nose which continually administers oxygen to improve airflow and breathing throughout the night. If the device fits poorly or loosens throughout the night, the airstream heading in the direction of the corneal surface can worsen symptoms of dryness, especially if concurrent lagophthalmos is present. In addition to the dryness risks associated with the CPAP machine, individuals with sleep apnea have an increased likelihood of having Floppy Eyelid Syndrome, an eyelid condition in which the lids are less taught than normal and may have the tendency to flip over. Floppy Eyelid Syndrome oftentimes means lids are unknowingly flipped open throughout the night, increasing the risk of corneal irritation. Improving nighttime dryness for those with sleep apnea may be as simple as adjusting a poorly fitting CPAP machine, or it may require drops and overnight ointments to prevent damage due to overnight exposure.
Continued overnight corneal exposure can not only cause discomfort, but may lead to significant damage to the front of the eyes. If you believe you have symptoms of nighttime dryness, visit your optometrist for evaluation and treatment.