Which instrument provides a quantitative measure of tear secretion?

The Schirmer test is specifically designed to quantitatively assess tear secretion. In this test, a small strip of filter paper is placed in the lower conjunctival sac of the eye, and the amount of moisture on the strip after a designated period is measured in millimeters. This provides a direct measurement of tear production, which is essential for diagnosing conditions related to dry eyes and other related issues.

In contrast, the tonometer measures intraocular pressure, which is crucial for detecting glaucoma but does not provide information about tear secretion. The keratometer measures the curvature of the cornea, mainly used for fitting contact lenses and assessing corneal shape, rather than tear production. The slit lamp is an instrument used for examining the anterior segment of the eye and can provide detailed views of eye structures, but it does not measure tear secretion quantitatively. Thus, the Schirmer test is the only instrument mentioned that directly measures tear production.