Mapping the Blockage: Biology and Diagnosis

When your eyes won’t stop watering, the first task for your doctor is to determine if the drainage pathway is physically blocked or if it is simply not working efficiently. This involves categorizing the type of blockage and performing a series of diagnostic tests to map out your unique anatomy.

Primary vs. Secondary Blockages

Doctors divide acquired tear duct obstructions into two main categories based on what caused them.

Primary Acquired Nasolacrimal Duct Obstruction (PANDO)

PANDO is the most common form ^[1]. It is considered “primary” because there isn’t one single external event that caused it. Instead, it is a multifactorial process where chronic, low-grade inflammation is associated with fibrosis (scar tissue) that slowly narrows the duct ^[1][2].

Secondary Acquired Nasolacrimal Duct Obstruction (SANDO)

SANDO occurs when a known external factor or underlying disease causes the blockage ^[3]. Common causes include:

• Medical Treatments: Radioactive iodine (often used for thyroid conditions), chemotherapy, or radiation therapy to the face ^[4][3].
• Trauma: Fractures to the bones of the face or nose ^[3].
• Inflammatory Diseases: Conditions like sarcoidosis or granulomatosis with polyangiitis ^[3].
• Tumors: While rare, growths in the sinus or tear sac can physically block the duct ^[5].

Distinguishing between PANDO and SANDO is vital because secondary causes sometimes require different treatments or have different surgical success rates ^[3].

The Diagnostic “Roadmap”

To find the exact location of a blockage, your doctor will perform a physical workup alongside specific tests.

Probing and Irrigation

The most common test is lacrimal irrigation ^[6]. The doctor places a tiny, blunt tube into the opening of the tear duct (the punctum) and gently flushes it with saline.

• The “Hard Stop”: This generally means the probe has successfully passed through the smaller upper tubes (the canaliculus) and contacted the medial wall of the lacrimal sac. It suggests the upper tubes are open ^[7].
• The “Soft Stop”: If the probe hits spongy tissue and cannot reach the sac wall, the blockage is likely higher up, in the smaller tubes called the canaliculi ^[7].
• Reflux: If the saline washes back out of the same hole or the hole next to it, the duct is obstructed ^[8].

Jones Dye Tests

These tests use a special yellow dye (fluorescein) to see how well your eyes drain naturally.

• Jones I: The doctor puts dye in your eye and waits a few minutes. If they can find the dye in your nose (usually by having you blow into a tissue), the test is positive, meaning the drain is open ^[9].
• Jones II: If the first test is negative, the doctor will flush the eye with saline. If the yellow dye appears in your nose during the flush, it suggests the system is physically open but functioning poorly ^[6].

Note: Jones tests have limited sensitivity and are interpreted as adjunctive clues alongside examination and irrigation; a negative Jones I does not perfectly establish whether a blockage is structural or functional.

Structural vs. Functional Blockage

A major goal of diagnosis is telling the difference between a structural blockage and a functional delay.

• Structural Blockage: There is a physical barrier of scar tissue or bone blocking the flow. Irrigation will usually fail ^[10].
• Functional Delay: The pathway is physically open (irrigation passes easily), but the tears aren’t moving. This can happen if the “tear pump”—the muscles that squeeze the tear sac when you blink—is weak ^[10][11].

Advanced Imaging: Seeing the Invisible

Advanced imaging is selected for particular clinical questions, trauma, suspected secondary disease, or unclear anatomy, and is not required for every routine patient:

• Dacryocystography (DCG): A specialized X-ray where a contrast dye is injected into the tear ducts to highlight the exact shape and location of a blockage ^[12].
• CT-DCG: Combines the dye test with a CT scan. This is excellent for seeing the bones and sinuses, especially if you’ve had a facial injury ^[13].
• MR-DCG: Uses an MRI to see the soft tissues and fluid, though protocols vary and are not routinely real-time dynamic studies ^[7][14].
• Dacryoscintigraphy (DSG): Uses a tiny amount of radioactive tracer to track how fast tears move through the system, which can provide useful transit information ^[15][16].
• Nasal Endoscopy: A tiny camera is placed in the nose to see if a polyp, a deviated septum, or a sinus issue is pressing on the tear duct from the outside ^[6][17].