Laserasi Duktus Lakrimalis

01Pathophysiology

The lacrimal drainage system begins at the puncta, small openings located on the medial aspect of both the upper and lower eyelid margins. Tears drain through the puncta into the superior and inferior canaliculi, which converge at the common canaliculus before emptying into the lacrimal sac, seated within the lacrimal fossa of the medial orbital wall. From there, tears flow through the nasolacrimal duct and exit beneath the inferior turbinate in the nasal cavity.

When a laceration occurs medial to the punctum on either eyelid, the canaliculus is at direct risk of transection. The inferior canaliculus is the primary drainage conduit, handling roughly 70% of tear outflow, which is why injuries to the lower lid medial to the punctum carry the greatest functional consequence. If the severed canaliculus is not identified and repaired, the cut ends will scar and fibrose, creating a permanent obstruction. The patient then develops chronic epiphora (overflow tearing) because tears can no longer reach the lacrimal sac and drain into the nose.

The reason dog bites are so frequently tested is anatomical: a dog's canine teeth tend to grasp and tear the medial canthal region of the face, and in children, the bite height aligns perfectly with the medial eyelid. This mechanism produces irregular, crushing wounds that often transect the canaliculus while also introducing infection risk from oral flora.

A laceration lateral to the punctum, by contrast, does not involve the drainage apparatus and can be closed primarily without concern for epiphora. This anatomical landmark is the single most important distinction the exam tests.

02Classification and Clinical Manifestation

Canaliculus Involved

03Diagnostic Workup

The workup begins at the bedside. Any eyelid laceration must be evaluated for its position relative to the punctum. If the wound is medial to the punctum, canalicular injury should be assumed until proven otherwise. A common pitfall is closing a medial eyelid laceration in the emergency department without first assessing the canalicular system, because the external wound may look deceptively simple.

Formal probing and irrigation is performed under magnification, ideally by an ophthalmologist. A lacrimal probe or small-gauge cannula is inserted through the intact punctum into the canaliculus. If the probe exits through the wound or saline irrigated through the punctum leaks from the laceration rather than reaching the nose, the canaliculus is confirmed to be transected.

CT imaging is not required for an isolated soft-tissue canalicular laceration but becomes necessary when the mechanism suggests midface fractures, such as high-energy blunt trauma or motor vehicle collisions. Naso-orbito-ethmoid fractures can disrupt the lacrimal sac or nasolacrimal duct at the bony level.

04Management and Treatment

The cardinal rule in the emergency setting is: do not close a medial eyelid laceration without first ruling out canalicular involvement. If the wound is medial to the punctum, the patient should be referred to ophthalmology or oculoplastic surgery for definitive repair rather than having the wound closed primarily by the emergency physician.

The repair itself involves identifying both cut ends of the canaliculus under an operating microscope. The distal (lacrimal sac) end can be located by irrigating through the opposite intact canaliculus and watching for fluid egress in the wound. A silicone stent is passed through the system to act as an internal scaffold, and the canalicular mucosa is reapproximated with fine absorbable sutures (typically 7-0 or 8-0 polyglactin). The overlying lid tissue is then closed in layers.

For dog bite wounds, antibiotic prophylaxis with amoxicillin-clavulanate is standard. Rabies post-exposure prophylaxis should be considered based on the animal's vaccination status and local epidemiology.

If the injury presents late (weeks to months later) with established scarring and chronic epiphora, primary repair is no longer feasible. The standard salvage procedure is a dacryocystorhinostomy, which bypasses the canalicular obstruction entirely.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The most common way students lose points on this topic is by failing to recognize that a medial eyelid laceration is not just a wound to close but a potential canalicular injury requiring subspecialty repair. The vignette will describe a patient with a laceration "near the inner corner of the eye" or "medial to the punctum," and the wrong answer will be primary wound closure in the emergency department. The correct answer is ophthalmology consultation for canalicular exploration and stented repair.

A second frequently tested trap involves the mechanism. When a child presents after a dog bite to the face with a wound near the medial canthus, students may focus on wound infection management and miss the canalicular injury. The exam expects you to recognize that the anatomic location of the wound, not just the etiology, determines the next step. Antibiotics address the bite, but the wound itself needs operative canalicular repair.

Finally, remember the timing window. Canalicular repair should be performed within 48 hours. A vignette describing a patient who presents days to weeks after injury with persistent tearing is testing whether you know that primary repair is no longer viable and that the answer has shifted to dacryocystorhinostomy.

The core competency being tested is anatomical reasoning: can you use the location of a wound relative to the punctum to predict which deeper structures are at risk and, from that, determine the correct management pathway?