When you sleep, your tear excretion system will work. If your eyes become dry, you may pay attention to the daytime dryness which is the main reason. You could eat more food with vitamin C to moisture the eyes. You could also use the eye drops to make your eyes keep moisture. During the sleep, you'd better not let the air condition blow at your face which could also make your eyes get dry.
There are many reasons to cause dry eyes such as decreased tear production, excessive tear evaporation, and an abnormality in the production of mucus or lipids normally found in the tear layer, or a combination of these. Some medications, such as antihistamines, antidepressants, beta-blockers, and oral contraceptives, may decrease tear production and then results in dry eyes. And if blinking is decreased or if the eyelids cannot be closed, the eyes may dry out because of tear evaporation. So if you spend much time reading, watching TV, or performing a task that requires close attention with the eyes, you may not blink as often, and this decreased blinking allows excessive evaporation of the tears, then you will feel dry eyes when you sleep. Some other certain conditions, such as stroke or Bell's palsy, make it difficult to close the eyes, as a result, the eyes may become dry from tear evaporation. Check which is the reason of your dry eye when you sleep.
Dry Eyes, is a condition many people confront. It is caused when the tears produced by the eyes are insufficient in moisture, lubrication, and other features that help keep the eyes remain protected. Based on dry eyes definition, we can easily conclude that your eyes are lace of tears and you may be dehydration. So before you go to bed, you can use moisturizing 'oil' for eyes and drink a big glass of water.