Canalicular laceration (Canalicular Laceration) is an injury caused by acute physical trauma to the canaliculus, part of the lacrimal drainage system. The canaliculus is located on the medial side of the eyelid, and because it does not include tarsal structure, it is easily torn near the medial canthus.
By site of injury, isolated lower canalicular laceration is the most common at about 71.9%. Isolated upper canalicular laceration accounts for 15.7%, and simultaneous injury to the upper and lower canaliculi or the common canaliculus accounts for 12.4%. The injury mechanism is broadly divided into indirect injury and direct injury.
The injury patterns are shown below.
Type of injury
Mechanism
Features
Indirect injury
Excessive lateral traction of the eyelid due to blunt trauma
Rupture on the nasal side and difficult to repair
Direct injury
Penetrating trauma from glass, metal, etc.; dog bites
The cut ends are relatively superficial
The ICD-10-CM codes are S01.111A for the right eye and S01.112A for the left eye.
QIs canalicular laceration more common in the upper or lower canaliculus?
A
Lower canalicular laceration is the most common, accounting for about 71.9%. Indirect injury (when the eyelid is pulled outward too far during a blow) causes a tear on the nasal side, so it is harder to repair and more difficult to operate on than a direct injury.
Preoperative and postoperative images of canalicular laceration and eyelid laceration
Guo T, et al. Eiology and prognosis of canalicular laceration repair using canalicular anastomosis combined with bicanalicular stent intubation. BMC Ophthalmol. 2020. Figure 2. PMCID: PMC7310031. License: CC BY.
Preoperative image (a) and postoperative image (b) after silicone tube insertion in a female patient with left lower canalicular laceration and full-thickness eyelid laceration; the tube is visible after surgery. This corresponds to canalicular laceration covered in section “2. Main symptoms and clinical findings”.
Lid laceration on the inner side of the punctum: the most important finding and a reason to suspect canalicular laceration right away.
Lateral displacement of the punctum: if the medial canthal tendon is also torn, the punctum shifts outward.
Widening of the wound: under slit-lamp microscopy, gently pulling the upper lid upward and the lower lid downward may open the wound and make the cut ends easier to see.
Canalicular cut end: appears as a shiny ring that is milky white or gray-white.
Bougie insertion finding: insert a bougie through the punctum and measure the distance to the laceration. A short distance suggests the distal end is superficial; a long distance suggests the cut end has retracted deep near the lacrimal sac.
Irrigation test finding: reflux confirms canalicular laceration.
Blunt trauma and fight-related injuries: the most common cause of canalicular trauma.
Dog bites: often occur near the medial canthus, and the rate of canalicular injury reaches 35.6%. This is markedly higher than the injury rate from other causes (3.6%). Pit bull terrier breeds are involved in many cases.
Blunt shearing injury: A bruise from a ball or a fall. Along with punches, this is a major cause.
Penetrating trauma: Direct injury from glass, metal, hooks on display shelves, or clothing fasteners.
Traffic accidents and falls: In older adults, the risk of injury from falls is especially higher.
As age- and sex-related risk characteristics, most injuries occur in children or young adults. Children under 4 years old are prone to facial dog bites, and older adults have a higher risk of falls. Men tend to have canalicular injuries more often than women. Reduced judgment due to alcohol and similar factors increases the risk of violence and traffic accidents.
The inner side of the eyelid does not contain the tarsal plate, so it tends to avulse when a force acts to pull it away from its attachments to the medial canthal ligament, lacrimal bone, or maxilla. With blunt trauma such as punches or ball impacts, tarsal rupture is uncommon, and the injury is more likely to be a laceration with canalicular rupture at the innermost part of the eyelid.
QHow often does canalicular rupture occur if a dog bites the face?
A
The rate of canalicular injury from dog bites is 35.6%, about 10 times higher than with other causes (3.6%). With bites near the inner corner of the eye, canalicular rupture should be strongly suspected, and early evaluation by an ophthalmology specialist is needed.
Imaging studies: If a retained foreign body is suspected, perform CT. MRI is contraindicated when a ferromagnetic foreign body is present.
Check for associated injuries: Evaluate for globe rupture, corneal perforation, orbital fracture, extraocular muscle injury, and head or facial trauma.
Even if only one side, upper or lower, is torn, lacrimal canalicular reconstruction is generally performed. The basic principle of surgery is to restore all separated tissues to normal anatomy as much as possible. There is consensus that all canalicular lacerations should be repaired as much as possible1).
Surgical repair within 48 hours after injury is preferred.
If it is within 1 week after injury, repair is relatively easy. It is also acceptable at the time of injury to close the wound only, prioritize other treatment, and perform reconstruction later.
Even in old cases, surgery is still indicated, but the more scarring progresses, the harder it becomes to identify the cut ends.
There have been successful cases even about 72 hours to 5 days after injury, so immediate emergency surgery is not always necessary.
General anesthesia: Preferred when the wound is extensive or accompanied by canalicular rupture. Local anesthesia causes tissue swelling, making it difficult to find the cut ends.
Local anesthesia: Use an infratrochlear nerve block together. Insert 1–2% lidocaine vertically along the orbital wall from just above the medial canthal tendon, and inject 1–2 mL.
Wound exposure: Use a skin hook or traction sutures (such as 4-0 silk) to expose the wound and search for the ends.
Hemostasis and field control: Use Bosmin gauze, bipolar cautery, and a suction tip to control bleeding while searching for the ends.
Check the cut end: The cut end of the canaliculus appears as a gray-white ring. After finding the end, confirm that it is the canaliculus by irrigation and probing.
If the end cannot be found: Reduce magnification, remove the retractors, infer the lacrimal sac-side end from the anatomical position, and search again.
② Tube placement
Monocanalicular stent: Mini Monoka and similar.
Bicanalicular stent: Crawford, Ritleng, and similar stents are placed from the punctum to the nasal cavity.
③ Canalicular suturing
End-to-end suturing: Suture with 2 to 3 stitches using 9-0 to 10-0 nylon or 8-0 absorbable suture. Start from the posterior wall and keep the knots facing outward. Tie after releasing the tension from the opened tissue.
Suturing the surrounding tissues: Suturing the surrounding tissues, including Horner’s muscle, together is important for functional reconstruction.
Medial canthal ligament: If it is torn, suture it (if left unrepaired, the punctum may shift outward and cause cosmetic deformity).
Skin closure: Close the subcutaneous tissue and skin with 7-0 nylon. Do not perform debridement, because it causes tissue loss.
④ Postoperative care
Eye drops: Start antibiotic and steroid eye drops from the day after surgery (the steroid is used to help prevent a foreign-body reaction to the tube).
Suture removal: Skin sutures are removed after 5–7 days (about 1 week).
Irrigation test: The first one is done about 2 weeks after surgery (doing it too early can cause leakage at the torn site and delay healing).
Tube removal: The tube is usually removed after 1–2 months, and then irrigation is checked every 2 weeks for the next 2–3 months.
In the case of an animal bite, consider the following.
Tetanus vaccine: If you have not been vaccinated within the past 10 years, give a booster.
Rabies management: Consider this in animal bites (especially wild animals).
Prophylactic antibiotics: Preventive treatment is recommended for bites that penetrate the skin. The first choice is amoxicillin/clavulanate (Augmentin). In dog bites, Pasteurella canis is a typical causative bacterium, and in cat bites, Pasteurella multocida is a typical causative bacterium.
QHow soon does surgery for a canalicular laceration need to be performed?
A
Repair within 48 hours after injury is considered desirable. If it is within 1 week, repair is relatively easy. Even old cases can still be surgical candidates, but the more scarring progresses, the harder it becomes to find the cut ends. Even immediately after injury, emergency surgery is not always necessary, and it is acceptable to plan the surgery after prioritizing the patient’s overall condition and any other injuries.
6. Pathophysiology and detailed disease mechanisms
The tear drainage system is made up of the punctum → vertical canaliculus (ampulla, about 2 mm) → horizontal canaliculus (about 8 mm) → common canaliculus (3–5 mm) → lacrimal sac in that order. The upper punctum is about 6.5 mm from the medial canthus, and the lower punctum is about 6.0 mm away. The cross-sectional area of the lower punctum is 0.321 mm² and that of the upper punctum is 0.264 mm², with no statistically significant difference1). The canalicular lumen is about 1–2 mm in diameter. A common canaliculus is present in 98% of patients, and in more than 80% of cases the upper and lower canaliculi join to form it.
Contraction of the pretarsal part of the orbicularis oculi muscle: This compresses the ampulla and shortens and compresses the canaliculi. It draws in tears by creating negative pressure while moving the punctum inward.
Contraction of the Horner (Horner-Duverney) muscle: This applies positive pressure to the lacrimal sac and nasolacrimal duct, pushing tears into the nasal cavity1).
During eye opening
Dilation of the canaliculi and lacrimal sac: Negative pressure is created, drawing in tears1).
Anatomical arrangement of the Horner muscle: It surrounds the canaliculi in a scissoring pattern, and around the horizontal canaliculus it runs more densely and in parallel (findings from electron microscopy and 3D histology)1).
The tear transit time through the upper and lower canaliculi is almost the same (and tear duct scintigraphy also shows no statistically significant difference), so if one side is impaired, the other can compensate to some extent1).
Clinical significance of unilateral canalicular obstruction
With unilateral canalicular obstruction alone, if eyelid position is normal, tears can be effectively drained through the healthy canaliculus. Fewer than 10% of patients with single canalicular obstruction experience epiphora under basal tear conditions1).
It has been reported that 75% of patients with failed lower canalicular repair did not develop epiphora (Ortiz and Kraushar)1). Smit and Mourits also reported no epiphora in all 16 cases of unilateral canalicular injury that were not repaired1).
Despite these compensatory mechanisms, the current consensus is that canalicular lacerations should be repaired whenever possible1). In addition to increased drainage through the healthy canaliculus, there is also a possibility of an autoregulatory mechanism in which punctal occlusion affects the interaction between the ocular surface and the lacrimal gland, reducing tear secretion1).
QIf only one canaliculus is lacerated, will tears always overflow?
A
Not necessarily. Fewer than 10% of patients with unilateral canalicular obstruction experience epiphora under basal tear conditions, and epiphora was also absent in 75% of failed lower canalicular repairs1). This is because the remaining canaliculus provides compensation. However, the current consensus is to repair it whenever possible.
7. Latest research and future outlook (reports at the research stage)
When part of the canaliculus remains after tumor resection, a procedure to marsupialize the residual canaliculus and use it as a tear drainage pathway is being investigated.
In a retrospective study of 22 eyes by Chiu et al., the epiphora rate after marsupialization was 9.1%, showing better results than the nonreconstructed group (reported epiphora rate in the literature: 12.5%/97 eyes)1).
Marsupialization may interfere with the capillary action of the lacrimal canaliculus and the Venturi effect. However, as a simple procedure that can avoid scar-related narrowing, it is being considered as an alternative in cases where complete repair is difficult1).
Anatomical clarification of the lacrimal pump mechanism
Studies using electron microscopy and 3D histology are gradually clarifying the precise anatomical relationship between the Horner-Duverney muscle and the lacrimal canaliculus. Detailed patterns of muscle fibers around the horizontal canaliculus are expected to help improve the precision of lacrimal drainage surgery1).
Mohammad Javed Ali, Raman Malhotra, Geoffrey E Rose, Bhupendra C K Patel. Holding back the tears: does marsupialisation of a remnant canaliculus after tumour resection help eliminate epiphora?. BMJ Open Ophth. 2022;7(1):e001090. doi:10.1136/bmjophth-2022-001090.
