A 55-year-old woman with dry eyes undergoes Schirmer's test without anaesthesia. At 5 minutes, the wetting of the strip measures 4 mm. Which statement is correct regarding this result?
- A It is within normal limits; normal wetting is ≥ 15 mm at 5 minutes
- B It is diagnostic of Sjögren syndrome regardless of other tests
- C It indicates severe aqueous deficiency; normal wetting is ≥ 10 mm at 5 minutes ✓
- D It is inconclusive; the test must be repeated with a topical anaesthetic
Correct answer: C. It indicates severe aqueous deficiency; normal wetting is ≥ 10 mm at 5 minutes
Explanation
Schirmer's test without anaesthesia measures basal plus reflex tearing. Normal wetting is ≥ 15 mm at 5 minutes. A value below 10 mm indicates aqueous tear deficiency; below 5 mm is severe. The patient's 4 mm reading confirms severe dry eye. Option A reverses the threshold. A low Schirmer value alone does not diagnose Sjögren syndrome; autoantibodies and other criteria are required.
Reference: The Eye: Basic Sciences in Practice / Bailey and Love's Short Practice of Surgery, Standard ed.
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