Tears drain into the lacrimal sac which sits close to the medial (inner) aspect of your eye. From here, they drain through the nasolacrimal duct into the nose (see here for an explanation of lacrimal anatomy).
Any part of the drainage pathway from the eye to the nose can be narrowed, often due to scarring of the ducts. Sometimes no narrowing is identified, but even in these cases, tears may not drain properly (functional obstruction).
Experienced sinus surgeons can open the lacrimal sac from inside the nose without needing to make any cuts to the skin on the outside. Sometimes a small tube (stent) is inserted for a few weeks after surgery to help keep it open.
This procedure is called an Endoscopic Dacryocystorhinostomy (EndoDCR).
Last updated 18/9/16