The normal production of aqueous tears is imperceptible to the eye. Excessive tearing can be extremely uncomfortable in a Dry Eye, and can be due to many different factors. There are at least three categories of tears that can cause tearing: reflexive tears, sympathetic tears, and emotional tears.
Reflexive tears are the kind of tears that are produced when the eyes become too dry, or if a foreign body falls into the eye. It is common to experience reflexive tearing in cold climates, or when performing activities that involve staring. Under these conditions, the oily layer of the tear film breaks up, and the aqueous layer evaporates. The eyes sense the lack of moisture, and spontaneously produce tears. Reflexive tears can be caustic. Although the near term sensation is wetness, which might feel good in an aqueous deficient eye, later the eyes can feel very irritated.
Sympathetic tears are tears produced in the eye opposite to the one that is experiencing discomfort. Sympathetic tearing is normal — we may get an eye lash in one eye, and the other eye tears. However, sympathetic tears can be alarming for people with Dry Eye because there may not be an obvious cause, and because sympathetic tears, like reflexive tears, can make an eye feel worse in the long run.
Emotional tears are produced because of emotions: joy, sadness, anger, etc. They are not as caustic as reflexive tears. However, to someone with Dry Eye, in the long run, they can cause considerable discomfort.