What is the Schirmer test, how is it performed, and how are abnormal results managed?

Schirmer Test

The Schirmer test is a diagnostic tool that measures aqueous tear production by placing a narrow filter-paper strip in the inferior cul-de-sac (typically the temporal one-third) and measuring the length of wetting in millimeters over a specified time period, but it should not be used as the sole criterion for diagnosing dry eye due to its variable results. 1

How the Test is Performed

The test involves placing a standardized filter-paper strip into the inferior conjunctival fornix, specifically the temporal one-third of the lower lid. The strip remains in place for a measured time period while tear production wets the paper. 1

Three Variations of the Test:

Schirmer I (Without Anesthesia):

• Performed without topical anesthetic
• Duration: 5 minutes
• Measures both basal and reflex tear secretion
• Diagnostic threshold: <5.5 mm of wetting after 5 minutes confirms aqueous tear deficiency 1
• Values <10 mm are suggestive of abnormality 1
• Values between 5-10 mm are relatively insignificant 1

Schirmer II (With Anesthesia/Basic Secretion Test):

• Performed with topical anesthesia
• Duration: 5 minutes
• Excess fluid must be gently removed from the cul-de-sac before inserting the filter paper 1
• <3 mm after 5 minutes is highly diagnostic of aqueous tear deficient dry eye 1
• 3-10 mm is considered equivocal 1
• This version gives more variable results than Schirmer I 1

Schirmer II Reflex Test:

• Filter paper inserted in inferior fornix
• Nasal mucosa stimulated with cotton-tipped applicator
• Duration: 2 minutes
• <15 mm after 2 minutes is abnormal 1

Interpreting Results

Critical Caveat:

The Schirmer test gives variable results and should never be used as the sole diagnostic criterion for dry eye. 1 An isolated abnormal result can be nonspecific, but serially consistent low results are strongly suggestive of aqueous tear deficiency. 1

The test has relatively poor specificity (51%) compared to other dry eye diagnostic tools 1, meaning it should always be interpreted within the context of symptoms and other clinical findings.

Management of Abnormal Results

When Schirmer test results are abnormal, management follows a systematic approach based on the classification of dry eye subtype 2:

Diagnostic Algorithm:

1. Schirmer I ≤5 mm/5 min without anesthesia → Confirms aqueous deficiency-type dry eye 2

2. Combine with meibomian gland dysfunction (MGD) examination:

   • Positive MGD + Normal Schirmer → Evaporative dry eye
   • Positive MGD + Abnormal Schirmer → Mixed-type dry eye 2
   • Negative MGD + Abnormal Schirmer → Pure aqueous deficiency

3. Use corneal fluorescein staining (CFS) to determine severity:

   • Level 1 (no staining) = Mild
   • Level 2 (<1/3 corneal staining) = Moderate
   • Level 3 (1/3 to 1/2 staining) = Severe
   • Level 4 (>1/2 staining) = Advanced 2

Important Clinical Pearls:

• The fluorescein dye disappearance test shows better correlation with symptom severity and corneal staining than the Schirmer test 1, making it a valuable complementary tool
• Consider tear osmolarity testing (cutoff 312 mOsms/L has 73% sensitivity and 92% specificity) for additional diagnostic confirmation 1
• Serial measurements over time are more clinically meaningful than single values, especially in milder disease 1

Common Pitfalls to Avoid:

• Do not diagnose dry eye based solely on one abnormal Schirmer test result
• Do not perform the test after instilling any eye drops, especially anesthetics (except for Schirmer II)
• Do not forget to remove excess anesthetic from the cul-de-sac when performing Schirmer II, as residual fluid will falsely elevate results
• Do not ignore patient symptoms when test results are borderline—the test has limitations in sensitivity and specificity