Crusty eyes in the morning is a common condition for children and adults alike. If it continues you should mention this to your children's doctor
on your next visit. As with any symptoms regarding the eye, they must be taken seriously. See your doctor emergently if there is any vision change, eye pain or redness in the eye. These warning symptoms may indicate a disease that could cause loss of vision.
The crusty eyes of the morning are often from eye discharge that builds up and subsequently dries out over night. Therefore the question is: why there is eye discharge? There is a normal amount of tears that your body produces to moisten and lubricate the eyes, therefore a small amount of discharge/crusty is expected. There are situations where people have increased eye discharge therefore increased crustiness. Eye infections, such as conjunctivitis, can cause this, either from a bacterial or viral cause. Usually this is one eye only. If this is the case than your doctor can treat this with eye drops, however this rarely is a chronic problem. Another possibility is allergies, which can increase eye discharge in both eyes. People can be allergic to common substance like laundry detergents or the pillow's filling
. Most of the time there will be other symptoms (runny nose or cough as well). In children, one other concern is that the tear drainage system has not developed fully. This occurs in 5% or so of babies but most children outgrow this.
While likely normal, the crusty morning eyes can be a sign of other eye conditions. Discuss your concerns with your children's doctor.