## **Core Concept**
The Schirmer's test is a clinical test used to assess tear production in the eyes. It measures the amount of tears produced by the lacrimal gland. The test involves placing a small strip of filter paper under the eyelid to absorb tears.

## **Why the Correct Answer is Right**
The correct answer, $geq 10$ mm, is considered normal because it indicates sufficient tear production. The Schirmer's test is typically performed over a 5-minute period, and a result of 10 mm or more of wetting on the filter paper strip is generally considered within the normal range. This suggests that the lacrimal gland is producing an adequate amount of tears.

## **Why Each Wrong Option is Incorrect**
* **Option A:** $<5$ mm - This value is considered abnormally low, indicating decreased tear production, which may be seen in conditions like dry eye syndrome or Sjögren's syndrome. * **Option B:** $5-9$ mm - This range is considered borderline or low, suggesting some degree of impaired tear production. * **Option D:** $geq 15$ mm - While values in this range are certainly normal, the question asks for the minimum normal value. ## **Clinical Pearl / High-Yield Fact** A key point to remember is that Schirmer's test results can be influenced by several factors, including the use of topical anesthetics (which can reduce tear production) and the time of day (tear production can vary). A normal result helps rule out conditions like dry eye, but abnormal results require further evaluation. ## **Correct Answer:** . $geq 10$ mm.