The nasolacrimal drainage system develops from cell tissue that originates in the nasal-optic fissure.
Development of the canal-type system (canalization) first occurs in the central area of the nasolacrimal passage and then proceeds both upward in downward. Normally, this process is completed by the end of the ninth month of gestation, but, occasionally, it may fail to form completely.
If canalization is incomplete, it most often occurs at the lower end of the nasolacrimal duct at Hasner’s valve. This causes tear outflow obstruction and is, by far, the most common cause for a nasolacrimal duct obstruction (NLD obstruction). There are other less common problems within the nasolacrimal system that can cause obstruction of tear outflow, including abnormal crowding or a bony obstruction of the nasolacrimal duct. Infants with a nasolacrimal duct obstruction present with a watery eye and an increased tear lake, mattering of the eyelashes, and mucus in the nasal cornea of the eyelids.
Congenital nasolacrimal duct obstruction is common and occurs in 1 to 5% of the population, with approximately 1/3 occurring in both eyes. If left untreated, approximately half of the cases will spontaneously open up by 6 months of age. After 13 months of age, the incidence of spontaneous resolution decreases to only 15%.
Management of NLD Obstruction
Significant controversy exists regarding the best timing for initial nasolacrimal duct probing. Some advocate probing even at a few months of age and suggest that it should be done in the office without anesthesia. Most pediatric ophthalmologist, however, suggest waiting until the child is at least 6 months of age, since almost half the children will have spontaneous resolution by then. Others suggest waiting until 1 or 2 years of age or longer before probing.
Medical management during the observational period is a combination of nasolacrimal sac massage and intermittent topical antibiotics.
Some suggest massaging down towards the nose to push the tears out the nasolacrimal duct, while others suggest massaging superiorly so the material exits the punctum. This author suggests using both methods. The initial massage is directed inferiorly to push the tears in the normal direction out the nasolacrimal duct.
Additional massage is directed superiorly, so that any tears that did not exit are at least cleared from the punctum. On occasion, inferior pressure itself will open a mild nasolacrimal duct obstruction. The use of topical antibiotic drops or ointments is indicated if there are signs of infection, such as mucopurulent discharge.
Nasolacrimal Duct Probing
For a normal obstruction, probing is a simple but delicate procedure. Under local or general anesthesia, a small steel wire is passed through the punctum into the nasolacrimal system, through Hasner’s valve, and down out the nose. In some cases, the inferior turbinate (tiny bone in the nose) is fractured to relieve crowding. This does not hurt, nor does it create any problem in the nose.
The success rate for a single nasolacrimal duct probing is approximately 90%. In cases where nasolacrimal duct probing fails, intubation with silicone tubes is indicated to establish a working system. Once inserted, the tubes are left in place for 1-3 months. Afterwards, the tubes can be removed in the office with local anesthesia. In general, silicone tubes are only used for patients who have failed the probing procedure and tearing persists.
Occasionally, probing and silicone tube placement does not resolve the symptoms associated with a nasolacrimal duct obstruction. Some patients will need to undergo infracture of the inferior turbinate, a small bony area that does not open at birth. This is done during a probing procedure and does not cause any pain or discomfort when the anesthesia wears off.