The tear duct is a channel/passage which runs from a tiny opening in the medial lids through the bone to the inside of the nose, and drains the tears and mucus the eye produces. It should open just before or just after birth but sometimes remains blocked for a considerable time after that, causing watering and discharge from the eye. It is harmless, and does not affect the health of the eye or the vision, although it can make the eyelids red and sore and slightly increases the frequency of infective conjunctivitis. The only potentially serious consequence is acute dacryocystitis, which is very unusual.

Most cases resolve with time and can be safely left to do so. Intervention is not normally considered under 1 year and even after that time, spontaneous resolution is still the most likely scenario. The procedure does not have to be done and the decision is the parents. The likelihood of probing success starts to decrease markedly after age 4 years. 

The aim of lacrimal probing is to open or widen the tear duct in order to reduce or eliminate watering and discharge