5.1 Goals

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  To review medial canthal and nasolacrimal anatomy relevant to the treatment of canalicular lacerations and medial canthal tendon avulsions.

  
  
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  To describe indications and contraindications for repair of medial canthal trauma.

  
  
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  To review key principles, surgical options, and stenting options in canalicular laceration repair, including pre- and postoperative considerations.

  
  
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  To review rescue maneuvers that can be employed if the lacerated ends of the canaliculus cannot be easily located.

  
  
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  To review tips and pearls relevant to the repair of medial canthal tendon trauma.

5.2 Advantages

The goal of oculoplastic repair of the medial canthal area is to restore the anatomic relationships of the eyelids, puncta, and canaliculi to the globe and nasolacrimal system. Surgical failure can be defined broadly as either failure of reapproximation of the lacerated canaliculi, or poor apposition of the eyelid and puncta to the globe in the form of medial ectropion. Accordingly, it is our preference to perform bicanalicular intubation of the nasolacrimal system whenever possible. To this end, we prefer to perform surgical repair in the operating room under general anesthesia. This approach provides the highest certainty of anatomic reapproximation of the canaliculi at the time of primary repair, allows adequate exploration of the medial canthal tendon complex and complete anatomic repair, and provides greatest patient comfort and cooperation during the procedure.

5.3 Expectations

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  Patients can expect minimal-to-moderate postoperative pain, bruising, swelling similar to other oculoplastic surgical procedures, depending on the extent of repair required.

  
  
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  Patients may experience postoperative tearing until the silicone stent is removed.

5.4 Key Principles

Essential to their function of modulating the healthy ocular surface environment by distributing the precorneal tear film, the eyelids must maintain proper position relative to the ocular surface and provide adequate lacrimal outflow. The components of a properly functioning lacrimal outflow system include patency and apposition of the marginal punctum to the ocular surface and tear lake, intact orbicularis oculi pump function, and patency of both the upper and lower segments of the nasolacrimal excretory system. In the context of trauma, care must be taken to ensure that these anatomic structure–function relationships are preserved, and when necessary, appropriately repaired.

Although in cases of monocanalicular trauma there is evidence that compensatory drainage through the contralateral canaliculus may be sufficient in draining basal tear flow, it has also been reported that over half of patients with monocanalicular obstruction will experience symptoms of watery eyes, blurred vision, redness, and crusting in situations of reflex tearing. ^{1 ,​ 2 ,​ 3} Furthermore, while there is a disagreement in the literature on the relative contributions of the upper and lower canaliculi to tear outflow, it can be concluded that there is variation between individuals and eyes, further advocating for repair of monocanalicular lacerations of either the upper or lower canalicular system. ^{2 ,​ 4 ,​ 5} Given the high success rates of monocanalicular repair of greater than 90%, it is our opinion that all monocanalicular lacerations should be repaired when possible. ^{6 ,​ 7}

As a concise review of the relevant anatomy, the upper and lower eyelid puncta are medial and lateral to the plica semilunaris, respectively, and have a diameter of approximately 0.3 mm at the mucocutaneous junction directed posteriorly into the tear lake. The puncta overlie the canaliculi, which travel approximately 2 mm vertically, turn medially at 90 degree angles, and travel 8 to 10 mm within the orbicularis oculi muscle (Fig. 5‑1). In the vast majority of individuals, the upper and lower canaliculi converge to form a common canaliculus before entering the posterolateral nasolacrimal sac deep and slightly superior to the anterior crus of the medial canthal tendon. ^{8 ,​ 9} Without support from the tarsus, which terminates near the punctum, the medial eyelid has only soft tissue support and is vulnerable to injury.

The medial canthal tendon has a close relationship with the lacrimal drainage apparatus. The preseptal and pretarsal orbicularis oculi fibers extend nasally to form the medial canthal tendon, which subsequently divides into anterior and posterior limbs. The anterior limb passes in front of the lacrimal sac and inserts on the anterior lacrimal crest of the maxillary bone. The posterior limb passes behind the lacrimal sac and inserts on the posterior lacrimal crest of the lacrimal bone. Stability of the posterior limb is disproportionately critical in maintaining the horizontal tone and posterior vector of the medial eyelid that keeps the eyelid punctum well apposed to the ocular surface and directed toward the tear lake.

Due to their relative proximity, concurrent injury to both the canaliculi and medial canthal tendon is common. A high index of suspicion for canalicular laceration or medial canthal tendon avulsion should be maintained in all cases of eyelid trauma, particularly when there is evidence of trauma medial to the punctum. As in all cases of trauma, history regarding the circumstances of the trauma should be collected whenever possible. Canthal avulsions and canalicular lacerations most commonly occur secondary to blunt trauma, animal bites, motor vehicle collisions, falls, and assault with lateral traction to the eyelid. They are often associated with avulsion of the medial canthal tendon. ^{10 ,​ 11 ,​ 12} Lacerations of the inferior system are more common than the superior. ^{6 ,​ 13} If injury is not identified and repaired in a timely fashion, insufficient lacrimal outflow with resultant epiphora and its associated ocular and visual symptoms may occur. Optimally, canalicular lacerations should be repaired within 24 to 48 hours, although there is evidence that acceptable outcomes may be obtained with delayed repair beyond 48 hours. ¹⁴ Adequate primary repair is crucial, as delayed repair to the canalicular system in symptomatic individuals may necessitate conjunctivodacryocystorhinostomy.

The key principles of successful canalicular laceration repair are identification of both ends of the lacerated canaliculus, canalicular reapproximation, canalicular intubation, and anatomic restoration of the eyelid margin position with adequate posterior vector of the medial canthus and posteriorly directed puncta into the tear lake. Practically speaking, surgical magnification is helpful, either through surgical loupes or an operating room microscope. In the case of concomitant medial canthal avulsion and canalicular laceration, intubation of the canaliculus should be performed first, followed by tendon repair.

In addressing the canalicular laceration, identification and location of the cut ends of the canaliculi must be performed preeminently. These cut ends appear as white or pink rings of mucosal tissue. Given the direction of the canalicular pathway, the more medial the laceration, the more posterior or deep the cut end of the canaliculus will be found. This is particularly true in the case of medial canthal avulsions, where the canaliculus may be avulsed at the level of the lacrimal sac. Copious irrigation, and gentle cleaning and debridement of the laceration using moist cotton tipped applicators, is useful. When performing the repair under general anesthesia, we prefer to avoid use of local anesthetic to evade distortion of the normal anatomy. Once both ends have been identified, the stent may be passed through the proximal and distal ends.

Regarding stent selection and canalicular intubation, several options exist, which may be broadly grouped into three categories: (1) bicanalicular intubation of the upper and lower canaliculi and nasolacrimal duct, (2) bicanalicular intubation of the upper and lower canaliculi alone, (3) monocanalicular intubation (Fig. 5‑2). It should be noted that excellent functional results can be obtained with a variety of the stents and surgical techniques. ^{6 ,​ 15 ,​ 16 ,​ 17 ,​ 18 ,​ 19 ,​ 20 ,​ 21 ,​ 22 ,​ 23} However, it is our preference, when possible, to perform bicanalicular intubation with a Crawford-type stent for both monocanalicular lacerations and bicanalicular lacerations as this may increase the likelihood of surgical success. ¹² Advantages include the strength of a closed loop stent, assurance of reapproximation of the lacerated ends, and a posteromedial directed vector of force that minimizes the risk of postoperative eyelid margin and punctum malposition.