The flow of the eyes is usually due either to an increased tear flow, a poor tear quality or to the fact that the outflow through the tear ducts does not work properly.
The reasons for an increased tear flow is that there is an irritation / pain in the eye for some reason. Examples of this are, misaligned hairs that abut the cornea (distichiasis / ectopic cilia / trichiasis), misaligned eyelids that do not close around the eye (entropion / ectropion), developmental disorders, foreign objects or wounds on the cornea / conjunctiva / eyelids.
Other causes can also be different types of eye inflammation, high pressure in the eye (glaucoma) or new growths that grow around or in the eye.
The tears consist of water, fat and mucus. A correct composition of the tears is important for a good tear quality and for them to function as a lubricant and protective for the eye. Too high a content of water produces “watery tears” that do not have the same ability to remain on the eye but give rise to watery eyes.
If the drain does not work, it may be due to a blockage in the tear duct. It can be caused by developmental disorders that are present from birth, “debris” that clogs the duct, damage or an infection. If the eyelids are not positioned correctly, so they fold inwards or outwards, the tears have a hard time finding the right way down into the tear ducts and instead the tear fluid chooses to flow outside the eye. They choose the “easiest” way.