What is a Seidel test on the eyes?

The Seidel Test for Ocular Wound Leaks

The Seidel test is a diagnostic procedure used to detect aqueous humor leakage from corneal or conjunctival wounds by applying fluorescein dye to the ocular surface and observing for a characteristic dilution pattern that indicates fluid leakage.

Purpose and Indications

• The Seidel test is primarily used to identify leaks from corneal or conjunctival wounds following trauma, surgery, or in cases of suspected perforation 1
• It helps evaluate the integrity of surgical wounds after procedures like cataract surgery 2
• The test is essential for detecting self-sealed perforations that might not be immediately apparent on examination 3

Test Procedure

Materials Required

• Fluorescein dye (strip or solution) 4
• Cobalt blue light (typically from slit lamp)
• Cotton-tipped applicator (if using fluorescein strip)

Step-by-Step Technique

1. Preparation of fluorescein:

   • If using a strip, moisten it with sterile saline solution and keep in contact for at least one minute to achieve adequate concentration 1
   • If using solution, use 1-2 drops of fluorescein solution directly 4

2. Application:

   • Apply the fluorescein to the suspected leak site or surgical wound 1
   • Ensure the dye covers the entire area of concern

3. Observation:

   • Examine the area using cobalt blue light from a slit lamp 1
   • A positive Seidel test shows a characteristic pattern: aqueous humor flowing from the wound dilutes and washes away the fluorescein, creating a clear streaming pattern within the yellow-green background 3, 5

Interpretation

• Positive Seidel test: Clear fluid stream appears within the fluorescein-stained area, indicating aqueous humor leakage 1
• Negative Seidel test: No streaming or dilution pattern observed, suggesting wound integrity is maintained 3
• Subtly positive: Sometimes the leak may be minimal and appear as a subtle dilution pattern that requires careful observation 1

Clinical Applications

• Post-surgical evaluation: Particularly after cataract surgery, penetrating keratoplasty, or other corneal procedures to ensure wound integrity 2, 5
• Trauma assessment: Evaluation of corneal or scleral injuries to detect perforations 3
• Bleb leaks: Detection of leakage from filtering blebs after glaucoma surgery 6
• Spontaneous leaks: Identification of spontaneous aqueous leakage in conditions like corneal ulceration 1

Variations and Alternatives

• Povidone-iodine technique (Siep's test): An alternative method using povidone-iodine drops instead of fluorescein to detect wound leaks, which has the added benefit of sterilizing the ocular surface 2
• Digital pressure: Gentle pressure on the globe may help reveal intermittent or low-flow leaks by temporarily increasing intraocular pressure 5
• Biosensor techniques: Emerging technologies using electrochemical detection of aqueous humor components like ascorbic acid can provide quantitative assessment of leakage 6

Precautions and Considerations

• Avoid tonometry: Non-contact tonometry should be avoided in cases of suspected corneal perforation as the air-jet can disrupt self-sealed wounds 3
• False negatives: Small or intermittent leaks may not be detected, especially if intraocular pressure is low 5
• Timing: The test should be performed before instilling any other drops that might wash away or dilute the fluorescein 1
• Interpretation challenges: Excessive tearing can dilute the fluorescein and make interpretation difficult 5

Documentation

• Record the location, size, and rate of any observed leakage 1, 5
• Document whether the leak is continuous or intermittent 5
• Note any associated findings such as shallow anterior chamber or hypotony 1