Many cases of tearing are due to loose lower eyelids. In some cases, it is obvious: the lower eyelids are so loose that they sag downwards and the tears simply pool up in the lids and then trickle down the face. However, some cases are observable only at the ophthalmic microscope. Each eyelid has a tear drain opening, located about 1/4 inch from the inner corner of the eye. This opening is normally turned inward. However, in some cases (as in the photo below), this drainage opening no longer fits up against the eyeball, and the tears have no place to drain to.
Finally, there are some cases in which there is no abnormality at all that you can capture with a simple photograph. In some people, the eyelids are just not tight enough. The tear drain system is a pump, and it relies on the eyelid muscles to squeeze the tear sac closed, drawing tears through the system like a suction bulb. The eyelid closure muscles wrap around the tear sac, so that whenever you blink, the tear sac is squeezed closed — open your eyes, and the tear sac opens, suctioning the tears off the surface of the eye. However, that mechanism no longer works if the lids are too loose. If your eyelids look normal and yet you still have tearing, this might be what’s going on. After a thorough separate examination of the tear drain system’s other components and a review of the health of the surface of the eye, a lower lid tightening may be your answer.