Schirmer Tests & Tear Break-Up Time

Schirmer Tests & Tear Break-Up Time

Quick Answer: Tear film testing determines whether a patient's tear volume and stability can support contact lens wear. Schirmer I (no anesthesia) measures basal plus reflex tearing — normal is >=10-15 mm of wetting in 5 minutes. Schirmer II (with anesthesia) isolates basal secretion; <5 mm is abnormal. The phenol red thread test is a faster, less irritating alternative. Tear break-up time (TBUT) measures tear film stability — normal is >=10 seconds, and <10 seconds indicates an unstable tear film that predicts contact lens intolerance, deposits, and staining.

Why Tear Film Testing Matters for CL

A contact lens floats on and within the tear film. Tear deficiency or instability causes:

• Lens awareness and discomfort — the leading cause of CL drop-out.
• Protein and lipid deposits — concentrated in poor tear films.
• Corneal and conjunctival staining — exposure keratopathy and 3-9 staining.
• Reduced wearing time and lens surface drying.
• Soft lens dehydration — low tear volume draws water out of the lens.

Schirmer Test I (Without Anesthesia)

Purpose: measures basal + reflex tear secretion.

Procedure:

1. Dry the eye of excess tears with a cotton-tipped applicator.
2. Fold a standardized Whatman #41 filter paper strip (5 x 35 mm) at the notch.
3. Place the folded end in the lateral third of the lower conjunctival fornix (not the caruncle).
4. The patient closes the eyes gently for 5 minutes (or looks downward).
5. Remove the strip and measure wetting from the notch in millimeters.

Interpretation:

A normal result effectively rules out aqueous deficiency; a low result prompts further work-up such as Schirmer II, osmolarity, or MMP-9 testing.

Schirmer Test II (With Anesthesia)

Purpose: isolates basal secretion by blocking reflex tearing.

Procedure:

1. Instill a drop of topical anesthetic (proparacaine or tetracaine).
2. Blot the remaining tears and excess anesthetic from the lower fornix.
3. Place the filter strip as in Schirmer I.
4. Wait 5 minutes and measure.

Interpretation:

• >=10 mm normal basal secretion
• 5-9 mm mild basal deficiency
• <5 mm abnormal basal secretion — aqueous-deficient dry eye

Schirmer II helps distinguish aqueous-deficient dry eye (Sjögren's, lacrimal gland disease) from evaporative dry eye.

Phenol Red Thread Test

A less-stimulating alternative to Schirmer.

• Use a cotton thread impregnated with phenol red (a pH indicator).
• Place the folded end in the lateral lower fornix for 15 seconds.
• Measure the wetted (red-colored) length in millimeters.
• Normal: >=10 mm wetting per 15 seconds.
• Abnormal: <6 mm.

Advantages: minimal reflex stimulation, faster, better tolerated — useful in sensitive patients and children.

Tear Break-Up Time (TBUT)

Purpose: evaluates tear film stability (not volume).

Procedure (fluorescein method):

1. Instill a small amount of fluorescein (dye strip moistened with saline, or a fluoret).
2. Ask the patient to blink a few times, then hold the blink open.
3. Examine with the cobalt blue filter on the slit lamp (or use a TearScope for non-invasive TBUT).
4. Start a timer at the last complete blink.
5. Stop at the appearance of the first dry spot (dark area) in the tear film.

Interpretation:

A TBUT <10 seconds suggests meibomian gland dysfunction or mucin deficiency and predicts CL intolerance.

Other Tear Film Tests (Brief)

• Tear osmolarity (>312 mOsm/L suggests dry eye; more specific than Schirmer).
• MMP-9 (InflammaDry) — elevated in inflammatory dry eye.
• Lipid layer evaluation (TearScope, interferometry) — assesses meibum quality.
• Meibography — imaging of meibomian gland structure.
• Rose Bengal / Lissamine Green staining — marks devitalized epithelial cells.

Applying Results to Contact Lens Fitting

Note on lens water content: paradoxically, high-water-content lenses can dehydrate faster in dry eyes, drawing tears from an already low reservoir. A low-water, silicone hydrogel lens with a surface wetting agent often performs better than a high-water traditional hydrogel.

Worked Clinical Scenario

A 52-year-old CL candidate reports afternoon dryness and blur with her current soft lenses. Work-up shows:

• Schirmer I (no anesthesia): 8 mm / 5 min — borderline low, indicating reduced total tear secretion.
• Schirmer II (with anesthesia): 6 mm / 5 min — mild basal deficiency (still above the 5 mm severe cutoff).
• TBUT: 6 seconds — unstable tear film; meibomian gland dysfunction suspected.
• Phenol red thread: 8 mm / 15 sec — mildly reduced.

Interpretation: this is a mixed aqueous-deficient and evaporative dry eye. Plan: lid hygiene and warm compresses for meibomian gland dysfunction, switch to a daily disposable silicone hydrogel with surface wetting agents, avoid extended wear, consider punctal plugs if symptoms persist, and re-evaluate after 4-6 weeks of treatment before authorizing continued CL use. Documenting these numbers in the chart supports your medical decision-making and protects the fitting as evidence-based.

Documentation Tips

• Record the test type, eye, time, and value (e.g., "Schirmer I OD 8 mm / 5 min without anesthesia").
• Note anesthetic used for Schirmer II so the basal-only result is not mistaken for a Schirmer I value.
• For TBUT, average three trials and record the mean; one short reading may be a blink artifact.
• Compare to baseline at follow-up visits to demonstrate treatment response or progression.