Dacryoscintigraphy

Dacryoscintigraphy, also known as Lacrimal Gland Scintigraphy, is a nuclear medicine procedure used to assess the functional patency of the lacrimal drainage system. It is most commonly performed in patients who present with epiphora, the excessive watering of the eyes. This condition typically results from partial or complete obstruction of the lacrimal outflow pathway, which hinders the natural drainage of tears from the eyes into the nasal cavity.  This diagnostic test offers valuable physiological information about how well the tears drain through the lacrimal passages and whether there is any blockage, functional delay, or abnormality in tear drainage. Unlike other anatomical imaging methods, dacryoscintigraphy is non-invasive, physiologically relevant, and causes minimal discomfort, making it suitable for both adult and pediatric patients.

What is Epiphora and Why is it Evaluated?

Epiphora is the involuntary overflow of tears onto the face, commonly caused by impaired drainage rather than overproduction of tears. It can occur due to a variety of reasons including aging, inflammation, congenital abnormalities, chronic infections, or trauma to the nasolacrimal duct.  The tears normally pass from the lacrimal glands to the puncta, then into the canaliculi, lacrimal sac, and eventually through the nasolacrimal duct into the nasal cavity. When there is a blockage or delay in this pathway, tears back up and overflow, causing discomfort, blurred vision, redness, and sometimes secondary infections. Accurate diagnosis of the site and severity of obstruction is critical for successful management and treatment, which may involve medication, stenting, or surgery.

What is Dacryoscintigraphy?

Dacryoscintigraphy is a dynamic radionuclide imaging test that uses a small amount of radioactive material to evaluate the tear drainage process in real time. Unlike anatomical methods like dacryocystography (DCG) or CT dacryography, which visualize the anatomy of the lacrimal passages, dacryoscintigraphy provides functional imaging, showing how tears move through the system over time.

The test is simple to perform and involves placing a drop of radiotracer near the eye (usually at the medial canthus or conjunctival sac) and then tracking its movement using a gamma camera. It allows ophthalmologists and nuclear medicine specialists to evaluate whether there is delayed transit, partial blockage, or complete obstruction of the nasolacrimal system.

Why is Dacryoscintigraphy Performed?

This scan is primarily used to diagnose and assess functional or anatomical blockages in the tear drainage system in patients complaining of excessive tearing or watery eyes. It is often the first-line investigation or used when anatomical imaging fails to identify the functional cause of epiphora.

Common Indications for Dacryoscintigraphy:

• Evaluation of chronic or unexplained epiphora
• Determining site of obstruction in lacrimal drainage pathways
• Diagnosing congenital nasolacrimal duct obstruction in infants
• Functional assessment of partial versus complete obstructions
• Post-surgical evaluation after dacryocystorhinostomy (DCR)
• Differentiating functional delay from true anatomical blockage
• Follow-up imaging to assess treatment efficacy
• Pre-operative mapping for planning lacrimal surgeries
• Screening in trauma-related lacrimal dysfunction

How is the Dacryoscintigraphy Test Performed?

The procedure is simple, quick, and generally non-invasive, making it an excellent outpatient diagnostic option. It is performed in a nuclear medicine department by trained technologists under the guidance of a nuclear medicine physician.

Step-by-Step Procedure:

1. Patient Preparation
   • No specific preparation is required
   • Patients should not apply any eye drops or cosmetics before the test
   • Contact lenses should be removed
   • A brief medical history is taken to understand symptoms and prior treatments
2. Radiotracer Administration
   • A small drop of radiotracer (commonly Tc-99m sulfur colloid) is instilled in the conjunctival sac near the inner corner of each eye
   • The dose used is very low and painless
3. Image Acquisition
   • The patient is positioned in front of a gamma camera
   • Dynamic imaging starts immediately and is recorded for 15 to 30 minutes, capturing the tracer's transit through the puncta, canaliculi, lacrimal sac, and nasolacrimal duct
   • Additional delayed images may be taken at 30 minutes or 1 hour, if needed
4. Patient Instructions During Scan
   • The patient is advised not to blink excessively
   • Blinking at normal intervals is encouraged to mimic physiological tear flow
   • Avoid rubbing or touching the eyes during the test

What Does the Test Show?

The gamma camera images provide clear evidence of how the radiotracer moves through the lacrimal system. By analyzing the time it takes for the tracer to pass through each segment, the physician can identify:

• Normal flow – tracer moves from eye to nasal cavity without delay
• Delayed flow – slowed drainage indicating partial blockage or dysfunction
• Stagnant tracer – suggesting complete obstruction of the nasolacrimal duct
• Asymmetrical flow – indicative of unilateral obstruction or functional asymmetry
• Post-surgical patency – verifying if DCR or other procedures were successful

Advantages of Dacryoscintigraphy

There are several distinct advantages that make dacryoscintigraphy a preferred test for investigating tear drainage issues:

• • Non-invasive and painless procedure
• • Low radiation exposure – safe for all age groups including children
• • Provides physiological evaluation of tear drainage under natural conditions
• • Quick and efficient outpatient test
• • Dynamic imaging – assesses function in real time
• • Detects functional abnormalities even in the absence of anatomical blockage
• • Useful in both diagnosis and post-treatment follow-up

Comparison with Other Tests

While imaging techniques like dacryocystography (DCG) and CT/MR dacryography show anatomical features, they often fail to reveal functional problems. Conversely, dacryoscintigraphy shows how the tears actually drain, making it invaluable when structural imaging is inconclusive.

This makes dacryoscintigraphy particularly useful in:

• • Idiopathic epiphora where anatomical tests are normal
• • Evaluating DCR surgical success
• • Pediatric cases where functional causes are suspected

Limitations and Considerations

Though highly useful, dacryoscintigraphy may have some limitations:

• It does not provide detailed anatomical imaging
• Not suitable for detecting fistulas or complex anatomical variants
• Requires cooperation of the patient, particularly in young children
• Interpretation can be subjective and depends on clinical correlation

Conclusion

Dacryoscintigraphy, or lacrimal gland scintigraphy, is a vital nuclear medicine procedure that provides functional insight into the patency of the lacrimal drainage system. It is an essential test for evaluating epiphora, especially when anatomical imaging fails to detect abnormalities. The test is non-invasive, safe, and physiologically accurate, making it ideal for both diagnosis and post-treatment assessment. It plays a significant role in the management of congenital and acquired lacrimal drainage disorders, particularly in children and elderly patients. When paired with clinical examination and, if needed, anatomical studies, dacryoscintigraphy helps deliver a complete picture for appropriate treatment planning and improved patient outcomes.