Lacerations of the canalicular system often occur in the setting of trauma. [1, 2] The canaliculi are the mucosal ducts through which tears drain from the eye.  The canalicular portion of the tear drainage system is in the medial aspect of the lid. The lacrimal drainage apparatus consists of the puncta on the upper lid and the lower lid, the canaliculi, the common canaliculus, the lacrimal sac, and the nasolacrimal duct.
Each eyelid margin can be divided into the larger palpebral portion (consisting of skin, orbicularis muscle, insertion of lid retractors, tarsal plate, and conjunctiva) and the smaller lacrimal portion (consisting of skin, orbicularis, canaliculi, and conjunctiva).  The palpebral potion of the lid is lined with lashes; posterior to the lashes are the openings of the meibomian glands of the tarsal plate. The palpebral margin assumes a flat contour. The lacrimal portion of the lid is round and without lashes. Injuries to the canalicular portion of the tear drainage system can occur as isolated injuries or as one component of more extensive injuries, including multiple marginal lid lacerations, orbital fractures, and globe injuries. 
Lacerations of the canalicular system result from direct or indirect trauma. [5, 6] Direct trauma includes severing the lacrimal portion of the lid with objects, such as glass, coat hangers, knives, dog bites, cat claws, fingernails, or other sharp objects. Indirect trauma results from blunt injury to the ocular adnexa from such mechanisms as blows to the face, blunt weapons, or falls onto blunt objects. 
Because of its superficial location in the medial lid, the canalicular system is vulnerable to trauma. The anatomy of the system includes the 2-mm vertical portion, which drains the puncta, and the 8-mm horizontal limb, which lies in the lacrimal portion of the lid, approximately 2 mm from the lid margin. The medial extent of the canaliculus interrupts the posterior arm of the medial canthal ligament. This ligament often is disrupted from the trauma and must be repaired to reestablish anatomic position and lid function.
Canalicular lacerations are the most frequent cause of injury to the lacrimal system. The inferior canaliculus is involved in more than 50-75% of cases. The horizontal lower limb is the most frequently involved site. In 2002, there were approximately 1.97 million visits to emergency departments for facial lacerations.  Lacerations to the canalicular system account for a very small percentage of these facial lacerations
A 2-year study of patients with eyelid injuries in Munich, Germany, found that 16% of eyelid lacerations involved the canalicular system.  A similar study in India showed that the canaliculus was involved in 24 (36%) of all eyelid lacerations. A 2006 survey of United Kingdom ophthalmologists showed that management of canalicular lacerations varies widely in the United Kingdom.  Eighty-three percent of the 92 UK surgeons repaired fewer than 5-10 canalicular lacerations per year.
If the canalicular system is not repaired initially, tearing can result from the disruption of the lacrimal anatomy, and the medial canthal area can have an abnormal appearance. Studies have demonstrated that both the inferior and the superior lacrimal drainage system can be instrumental in proper function of the tear drainage system. Primary repair can restore both lid function and position. Once the microscopic lacrimal system is scarred, it cannot be functionally repaired.
Race has not been reported to be a factor in trauma to the canalicular system.
Canalicular lacerations are most common in young adults. Canalicular lacerations in toddlers frequently result from dog bites. The mean age range is reportedly 18-30 years.
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