Why do tears form?
The short answer
Tears keep the eye surface moist, wash away particles, and maintain the conditions the cornea needs.
How it works
Basal tears spread over the eye all the time. Reflex tears from irritation and emotional tears are other forms, with differences in amount and composition.
A familiar example
Tears can also respond to irritation, such as smoke or a cut onion. Learn how cutting an onion triggers tears.