The outer lipid layer is an oily film that seals the tear film on the eye and helps to prevent evaporation. Tears are formed in several glands around the eye. The water layer is produced in the lacrimal gland , located under the upper eyelid. Several smaller glands in the lids make the oil and mucus layers. With each blink, the eyelids spread the tears over the eye.
Excess tears flow into two tiny drainage ducts in the corner of the eye by the nose.
These ducts lead to tiny canals that connect to the nasal passage. The connection between the tear ducts and the nasal passage is the reason that crying causes a runny nose. In addition to lubricating the eye, tears are also produced as a reflex response to outside stimulus such as an injury or emotion. However, reflex tears do little to soothe a dry eye, which is why someone with watery eyes may still complain of irritation. Dry eye syndrome has many causes.