In our eyelid there is a thing called tarsal gland, which can secrete grease all the time. Though people close eyes for a long time during sleeping time, the grease is still in secretion, and mixed with the impurities from tears and dust that into the eyes during daytime, then eye boogers form. It is not a disease if the quality of eye boogers is small. But if the eye boogers increases suddenly, even make the eyelid and eyelash stick together and you hardly open eyes, you may suffer from some eye diseases, caused by bacteria infection, and then you should go to the hospital treatment.
It's common for everyone to have eye dust in the morning that is called eye boogers. The tear is made up of water, protein, oils and mucin, which cover the surface of the eye to moisten and protect it. Usually, when we're awake, blinking washes rheum and tears away so that the eye boogers would be appear in eyes in the morning. And rheum can build up along with eyelashes or in the corner of the eye. However, your eyelids aren't blinking when eyes are closed thus the dirt and debris are diluted without cleaning by tears. Hence, it's easy to accumulate eye boogers on the outer corner of the eyes. The best way to clean eye boogers is using a washcloth with warm water to moisture the eyelid and eyelashes for a minute to clean them off.
If the quantity of the eye boogers is small, it belongs to the normal situation. One thing of tarsal gland in our eyelid may secrete grease all the time. Even during sleeping, the grease is still in the process of secretion. And the eye boogers are the forms of mixed impurities of tears and dust in the daytime. And this secretion is good for the eyes. However, if the amount is over the normal quantity which may stick your eyelid or eyelash, you should go to see the doctor because your eyes may get infected.