The eyelids contain many small oil glands -- in fact, there is one oil glands for each eyelash. These glands can easily be blocked off by an overgrowth of bacteria that can otherwise live in the eyelid normally. This can cause a disruption in the normal oil layer of the tears, producing many of the symptoms of dry eyes. In addition, the blockage of the oil glands can result in the production of "sleep" on the lids, either overnight, or while awake.
This condition is a very common reason that patients present to the ophthalmologist. Because there can be a variety of causes, the treatment must be individualized to the particular patient. What may seem like a minor annoyance, can become a chronic problem if not properly treated.