Epiphora is defined as the overflow of tears. The clinical spectrum of epiphora ranges from the occasionally bothersome trickle to the chronically irritating overflow. Epiphora is caused by a disruption in the balance between tear production and tear drainage. The lacrimal drainage system is a continuous and complex membranous channel whose function is dependent on the interaction of anatomy and physiology.
When faced with a patient who complains of tearing, the first step is to determine whether the epiphora is caused by an increase in lacrimation or a decrease in tear drainage. Trichiasis, superficial foreign bodies, eyelid malpositions, diseases of the eyelid margins, tear deficiency or instability, and cranial nerve V irritation may cause an abnormal increase in tear production. In the absence of these conditions, an abnormality in tear drainage is the most likely cause.
Abnormalities of tear drainage may be subdivided further into functional and anatomical. Functional failure is related to poor lacrimal pump function, which may be due to a displaced punctum, eyelid laxity, weak orbicularis, or cranial nerve VII palsy. Anatomical obstruction may occur at any point along the lacrimal drainage pathway and may be congenital or acquired. Congenital obstructions tend to produce symptoms during the neonatal period and are the subject of another article, Nasolacrimal Duct, Congenital Anomalies.
Classification of nasolacrimal drainage obstruction
The 2 types of acquired nasolacrimal drainage obstructions (NLDO) are primary and secondary. In 1986, Linberg and McCormick coined the term primary acquired nasolacrimal duct obstruction (PANDO) to describe an entity of nasolacrimal duct obstruction caused by inflammation or fibrosis without any precipitating cause.  Bartley proposed an etiologic classification system for secondary acquired lacrimal drainage obstruction (SALDO) based on published cases. [2, 3, 4]
PANDO is more common in middle-aged and elderly females. Using CT scans, Groessl and colleagues demonstrated that women have significantly smaller dimensions in the lower nasolacrimal fossa and middle nasolacrimal duct.  They noted that changes in the anteroposterior dimensions of the bony nasolacrimal canal coincide with osteoporotic changes throughout the body. These quantitative measurements may help explain the higher incidence of PANDO in women. Others have suggested menstrual and hormonal fluctuations and a heightened immune status as factors that may contribute to the disease process. These may explain the prevalence in middle-aged and elderly females. Hormonal changes that bring about a generalized de-epithelialization in the body may cause the same within the lacrimal sac and duct. An already narrow lacrimal fossa in women predispose them to obstruction by the sloughed off debris.
The general categories of causes of SALDO include infectious, inflammatory, neoplastic, traumatic, and mechanical. Bacteria, viruses, fungi, and parasites have been implicated as causes of infectious lacrimal drainage obstruction.
Viral causes of obstruction most commonly are seen with herpetic infection. The obstruction is due to the damage of the substantia propria of the canalicular elastic tissue and/or the adherence of the inflammatory membranes to the raw epithelial surface of the canaliculus.
Fungi may obstruct lacrimal passages by forming a stone (dacryolith) or cast. Parasitic obstruction is rare but is reported in patients infected with Ascaris lumbricoides, which enters the lacrimal system through the valve of Hasner.
Inflammation may be endogenous or exogenous in origin. Wegener granulomatosis and sarcoidosis are 2 examples of conditions that lead to obstruction due to progressive inflammation within the nasal and lacrimal sac mucosa. Other endogenously arising inflammations associated with lacrimal obstruction are cicatricial pemphigoid, sinus histiocytosis, Kawasaki disease, and scleroderma.
Exogenous causes of cicatricial lacrimal drainage obstruction are eye drops, radiation, systemic chemotherapy, and bone marrow transplantation.
The use of I(131) for thyroid carcinoma is associated with a 3.4% incidence of documented NLDO and an overall 4.6% incidence of documented or suspected obstruction.
Canalicular and nasolacrimal duct obstruction is a common adverse effect of weekly docetaxel therapy used for metastatic breast cancer and non-small cell lung cancer.
Neoplasms may cause lacrimal obstruction by primary growth, secondary spread, or metastatic spread. Primary neoplasms may arise in the puncta, canaliculi, lacrimal sac, or nasolacrimal duct. Secondary spread from nearby tissues is more common than primary tumors. They are most commonly eyelid cancers (eg, basal cell carcinoma, squamous cell carcinoma), although spread from the maxillary antrum and the nasopharynx also have been reported. Studies have documented oncocytoma and cylindroma from direct extension. Metastatic spread, an extremely rare phenomenon, has been reported with primary sites from the breast and prostate.
Trauma may be iatrogenic in the case of scarring of the lacrimal passage after overly aggressive lacrimal probing. Iatrogenic causes of NLDO also may follow orbital decompression surgery, paranasal, nasal, and craniofacial procedures. Noniatrogenic traumatic causes are either blunt or sharp and most commonly involve the canaliculus, lacrimal sac, and nasolacrimal duct.
Posttraumatic dacryostenosis was found to have a frequent association with delayed treatment of facial fracture repair or bone loss in the lacrimal district.
Mechanical lacrimal drainage obstructions may be due to intraluminal foreign bodies, such as dacryoliths or casts. These may be caused by infection (eg, Actinomyces, Candida) as well as long-term administration of topical medications. Mechanical obstruction also may be caused by external compression from rhinoliths, nasal foreign bodies, or mucoceles.
Dentigerous cyst in the maxillary sinus has been reported to have caused nasolacrimal duct obstruction.
This condition is relatively common, but the exact frequency is not known.
The incidence rate worldwide is unknown.
Epiphora can be a nuisance; if untreated, nasolacrimal duct obstruction can cause significant problems.
No predilection to race has been established.
PANDO is more prevalent in women. SALDO has no sexual predilection.
Previous studies have noted a high incidence of PANDO in individuals aged 50-70 years.
Surgical treatment provides resolution of primary acquired nasolacrimal duct obstruction in 85%-99% of cases.
Patients should be aware that epiphora caused by nasolacrimal duct obstruction is surgically treatable. Early recognition of secondary causes may provide the patient with more conservative treatment options.
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