The thin outer layer, produced by the inside of the eyelids, is an oily film. The largest part of the tear structure is a middle layer of salty water, produced in the lacrimal gland. The innermost layer, produced by the conjunctiva on the front of the eye, is composed mostly of mucus. This wonderfully designed film is ideal to protect, cleanse, and lubricate the eye . It circulates across and drains down a pinpoint opening at the inside corner.
Tears then flow through the nasolacrimal duct into the nose.
In many babies the nasolacrimal duct is not fully developed at the time of birth . Signs of this usually appear in the first weeks of life . The tears back up, causing wetness or pooling. As the watery layer evaporates, a soft mucoid discharge accumulates, which can then dry and become crusty. Sometimes the surrounding skin becomes red from irritation.