Swelling at the medial canthus, the inner corner of the eye nearest the nose, is a common occurrence that can range from a minor issue to a significant underlying problem. This area is the hub of the eye’s tear drainage system, meaning any disruption often manifests as noticeable swelling. Understanding the specific anatomy of this region and the mechanisms behind the swelling helps determine when the condition requires medical attention. This article explains the structures involved, the primary causes, signs of severity, and typical approaches to diagnosis and management.
Anatomy of the Inner Eye Corner
The medial canthus is the precise point where the upper and lower eyelids converge near the bridge of the nose. This location is associated with the lacrimal apparatus, the complete system responsible for producing and draining tears. Tears are collected by tiny openings on the inner edge of each eyelid, known as the puncta.
From the puncta, tears enter small tubes called the canaliculi, which then empty into the lacrimal sac, a reservoir situated next to the nose. This sac is where swelling is most often noticed. Tears finally drain from the lacrimal sac through the nasolacrimal duct, which extends downward into the nasal cavity.
When the nasolacrimal duct becomes blocked, tears and debris cannot drain properly, causing the lacrimal sac to become distended. This stagnation of the fluid provides an environment for bacteria to multiply, leading to the inflammation and swelling observed at the inner corner of the eye.
Leading Causes of Swelling
The most frequent cause of swelling is an infection of the lacrimal sac, known as dacryocystitis. This infection is almost always a secondary result of a blockage in the tear drainage pathway, most often the nasolacrimal duct. The obstruction creates a pool of stagnant tears, which then becomes colonized by bacteria like Staphylococcus aureus or Streptococcus pneumoniae.
Nasolacrimal Duct Obstruction (NLDO) itself is a factor, even without immediate infection. In adults, NLDO is often acquired, resulting from age-related narrowing, trauma, or inflammation from conditions like chronic sinusitis. The mechanical backup of fluid alone can cause a non-infectious, cystic swelling called a mucocele.
Another potential cause is preseptal cellulitis, a bacterial infection of the eyelid and surrounding skin confined to the front part of the eye socket. While this infection can occur anywhere on the eyelid, it frequently starts in the medial canthal area. Unlike simple dacryocystitis, preseptal cellulitis involves a more diffuse redness and swelling of the entire eyelid region.
Less common causes include tumors of the lacrimal sac, which can mimic a blockage and present as a mass. Allergic reactions and trauma to the nose or face can also lead to temporary, localized edema and inflammation. A firm and fixed mass may suggest a more serious underlying pathology.
Recognizing Accompanying Symptoms and Severity
Swelling at the medial canthus can be categorized as acute (sudden and painful) or chronic (milder and long-lasting). Acute dacryocystitis is characterized by intense pain, noticeable redness (erythema), and a tender, firm swelling directly over the lacrimal sac. This is often accompanied by epiphora, or excessive tearing, because the tears cannot drain past the obstruction.
A highly specific sign is the regurgitation of thick, pus-like or mucoid material from the puncta when light pressure is applied to the swollen area. Chronic cases typically present only with persistent tearing and intermittent discharge, with little pain or significant swelling.
Signs that indicate the infection is spreading beyond the immediate area require immediate medical attention. These indicators include a fever, vision changes, or pain when moving the eye. The spread of infection into the tissues behind the orbital septum, known as orbital cellulitis, is a serious complication that can threaten vision and lead to systemic issues like meningitis. Any rapid worsening of symptoms or the development of a firm, fixed mass should be addressed by a healthcare professional.
Diagnosis and Management Approaches
Diagnosis begins with a thorough physical examination, where the doctor assesses the swelling, looks for redness, and gently palpates the area to check for tenderness and discharge. The regurgitation of pus upon pressure over the lacrimal sac is a significant clinical indicator of dacryocystitis. If discharge is present, a sample may be collected to culture the bacteria and determine the most effective antibiotic.
Imaging tests, such as a CT scan, are sometimes used to identify the exact location and cause of a blockage, particularly if trauma, tumor, or an underlying sinus issue is suspected. Management depends on the severity and cause. Mild, acute infections are often treated with a course of oral antibiotics, typically for seven to ten days, along with frequent warm compresses to help reduce swelling and discomfort.
For severe infections accompanied by a high fever or systemic symptoms, intravenous antibiotics may be required, often necessitating a hospital stay. If an abscess has formed, a doctor may perform a controlled incision and drainage to relieve pressure and remove the accumulated pus.
Once the acute infection has resolved, chronic or recurrent blockages usually require a surgical procedure called dacryocystorhinostomy (DCR). The DCR procedure creates a new drainage pathway between the lacrimal sac and the nasal cavity, bypassing the original obstruction. This surgical intervention is the definitive treatment for chronic dacryocystitis and prevents repeated episodes of infection. In congenital cases in infants, a probing procedure can sometimes open the membrane causing the obstruction.