The tear ducts may become obstructed at any point between their entrance at the inner corner of the eyelids and their final opening into the nose (See image in panel 2 below).

Children may be born with a tear duct that has not fully opened (congenital nasolacrimal duct obstruction).  Most open spontaneously within the first 18 months of life.
Obstruction of a previously open tear duct in adults most commonly is due to blockage of the nasolacrimal duct, sometimes following infection though usually for no apparent reason.   Other causes include trauma, previous surgery (eg sinus surgery), chemotherapy or radiotherapy, or problems within the nose.  Obstruction may also occur at the entrances to the tear system (punctal occlusion) or within the early parts of the tear duct (canalicular obstruction).

Watering, usually constant if complete obstruction present, worse if cold or windy; tends to run down next to the nose.
Discharge or stickiness of the eye often present with nasolacrimal duct obstruction.
Enlargement of the lacrimal sac may follow nasolacrimal duct obstruction, leading to a lump in the inner corner of the eye from which mucus can be expressed on pressure (mucocele).
Infection of the stagnant contents of the lacrimal sac causes dacrocystitis, producing a painful inflamed lump in the inner corner of the eye that may rupture and discharge pus on to the skin.

Dacrocystitis requires rapid antibiotic treatment.

Congenital nasolacrimal duct obstruction that fails to improve spontaneously by 18 months of age is likely to remain permanently obstructed without treatment.  Passing a probe down the tear duct then has a high chance of opening the tear duct (approximately 90%).  This is carried out under a brief general anaesthetic as a day case.  If watering persists it can be repeated, usually with placement of a silicone stent to hold the passage open whilst it settles from the surgery.  This remains in place for several months before removal, again with a brief general anaesthetic.  Occasionally a DCR procedure is required (see below)

Adult nasolacrimal duct obstruction does not respond to probing.  A new tear passage is needed between the lacrimal sac and the nose (a DCR procedure).  In the past this was generally carried out via a small incision on the skin on the side of the nose.  My audited results using this technique show a success rate of at least 95%.  Increasingly I am now performing surgery via the nose (endoscopic DCR) with a very high success rate.  This approach minimises trauma and avoids a skin incision.  Most surgery is carried out under a general anaesthetic as a day case.  A silicone stent is usually placed and removed in clinic 1-3 weeks later.

Occlusion of the entrances to the tear system is treated by a small operation to provide an opening using local anaesthesia as a day case procedure.

Obstuction of the canalicular portion of the tear system generally requires placement of a small glass drain-pipe (Jones tube) which drains tears directly from the inner corner of the eye to the nose.  This is performed under a general anaesthetic as a day-case.

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