Half-open eyes during sleep are not caused by large eyes, but by a medical condition known as incomplete eyelid closure. This is a condition that can cause dry eyes, tearing, conjunctival congestion, exposure keratitis, corneal ulcers, etc. If you are sleeping with your eyes half open, you should go to the hospital to find out the cause and get targeted treatment. 1. Nerve palsy: When the facial nerve is paralyzed, the orbicularis oculi muscle is paralyzed, causing the lower lid to droop and the eyelid to close incompletely. If it does not improve for a long time, you should go to the hospital for symptomatic treatment; 2. Scar ectropion: caused by inflammation, ulcers, trauma causing skin defects in the eyelid area, or scarring in the eyelid area causing scar ectropion, which can be surgically corrected at this time to restore the normal structure of the eyelid and relieve symptoms; 3. Protruding eyeballs: disproportion between orbital volume and eye size, such as thyroid-related eye disease, The protrusion of the eyeball caused by congenital glaucoma, corneoscleral grapheme and orbital tumors results in incomplete eyelid closure. The cause should be treated to stop the protrusion of the eyeball and relieve the eyelid closure insufficiency; 4. Functional eyelid closure insufficiency: In a few normal people, a gap in the lid fissure can also result from reduced tone of the orbicularis oculi muscle during sleep, but part of the eyelid is already closed and the eye no longer receives light stimulation, which usually does not affect sleep and does not require special treatment; 5. Temporary eyelid closure insufficiency: Temporary eyelid closure can occur during general anesthesia or severe coma. Temporary eyelid closure can occur during general anesthesia or severe coma and can improve after the problem is resolved. It is recommended that patients with eyelid closure insufficiency should take early and effective measures to protect the cornea before the cause is identified or removed, such as applying erythromycin ointment to the conjunctival sac, traction of the upper and lower lids to bring them close to each other, and use of eye pads to cover the eyes to avoid further aggravation of the condition.