The canaliculus is a small part of the eye’s anatomy, contributing to eye health and comfort. It ensures proper tear flow, maintaining clear vision. Problems with the canaliculus can cause discomfort and visual issues.
Understanding the Canaliculus and Tear Drainage
The canaliculus consists of a pair of tiny channels, one in the upper and one in the lower eyelid, located at the inner corner of each eye. These tubes begin at the lacrimal punctum, a pinpoint opening on the eyelid margin. Each canaliculus descends or ascends vertically for about 2 millimeters before bending medially to run horizontally towards the lacrimal sac.
These channels are part of the lacrimal drainage system, managing tears produced by the lacrimal and accessory glands. Tears spread across the eye’s surface, providing lubrication, flushing out debris, and supplying oxygen to the cornea. The tears then gather at the medial angle of the eye, near the nose.
From this collection point, tears enter the puncta and flow into the canaliculi. The superior and inferior canaliculi join to form a common canaliculus, which empties into the lacrimal sac. This sac, located beside the nose, is a reservoir before tears drain into the nasal cavity via the nasolacrimal duct. The orbicularis oculi muscle, surrounding the canaliculi, contracts during blinking, creating a pumping action that moves tears into the lacrimal sac.
Common Issues Affecting the Canaliculus
Problems with the canaliculus can disrupt tear drainage, leading to various uncomfortable symptoms. One common issue is canaliculitis, an inflammation or infection of the lacrimal canaliculus. It is often caused by bacteria (e.g., Actinomyces israelii), but fungi (e.g., Candida species) or viruses (e.g., herpes simplex) can also be responsible. Punctal plugs, used for dry eyes, may also migrate and cause infection.
Canaliculitis often causes excessive tearing (epiphora) and a sticky or purulent discharge. The area around the canaliculus may be red, swollen, and tender. The punctum may also become enlarged or everted, known as a “pouting punctum.” These symptoms arise because the inflammation obstructs the normal flow of tears.
Another common issue is canalicular stenosis or obstruction, a narrowing or blockage of these tear drainage channels. This can result from various factors, including certain chemotherapy drugs, radiation exposure near the eyes, or chronic inflammatory eye conditions like conjunctivitis. Physical trauma or infections such as herpes can also contribute to the narrowing. When narrowed or blocked, tears cannot drain effectively, leading to persistent watery eyes and irritation.
Treatment Approaches for Canaliculus Problems
Accurate diagnosis is the first step in addressing canaliculus problems. A medical professional performs a physical examination, assessing symptoms and the appearance of the eyelids and the area near the nose. Lacrimal probing and irrigation are common diagnostic procedures, where a thin probe is inserted into the canaliculus and saline solution is flushed through to check for blockages or patency. Imaging studies, such as dacryocystography, CT scans, or ultrasound biomicroscopy (UBM), may also be used to visualize the tear drainage system and identify abnormalities. If an infection is suspected, cultures of discharge or tissue samples can help identify the microorganism.
Treatment for canaliculitis often begins with conservative measures, including the application of warm compresses to the affected area. Topical antibiotic eye drops or ointments are frequently prescribed, and oral antibiotics may also be necessary to combat the infection. If these medical treatments are insufficient, a surgical procedure called a canaliculotomy may be performed to open the blocked duct and remove any infected material or concretions.
For canalicular stenosis or blockages, several interventions are available. Less invasive options include dilation and irrigation to widen the narrowed channel. A punctoplasty is a surgical procedure specifically designed to widen the punctal opening. In many cases, a temporary silicone stent may be inserted into the canaliculus to keep the duct open during the healing process, helping to maintain tear flow.
For more extensive or complex blockages affecting the broader tear drainage system, such as those involving the lacrimal sac or nasolacrimal duct, a dacryocystorhinostomy (DCR) may be performed. This surgery creates a new pathway to allow tears to drain directly into the nasal cavity, bypassing the obstruction. Consulting with a medical professional is recommended for a proper diagnosis and personalized treatment plan.