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Grades K–2 · Organisms

Why do we blink even when we are not sleepy?

Your eyes need a thin, wet coat of tears even when you are not crying. This coat helps the front of each eye stay smooth and moist. It also helps protect the eye from dust and other irritating things.

O65 visual explanationA simplified eye in the reopen stage of a blink. Tears are present without crying; the moving lid spreads their film. A marker near the inner corner shows a drainage opening. No tear quantity or blink timing is calculated.A blink spreads a thin tear coatThe eye opens with its wet coatDrain openingBlue line: transparent tear coatTears help the eye stay smooth and moist.

In the diagramA blink spreads a thin tear coatThe eye opens with its wet coatDrain openingBlue line: transparent tear coatTears help the eye stay smooth and moist.

A blink spreads a thin tear coat; the reopened eye remains moist.

When you blink, your eyelid moves across the eye. It spreads tears over the clear front surface. When the lid opens again, the wet coat is still there. You do not have to cry for tears to do this job.

Glands help make the tears. Small openings near the inner corner of the eye let tears drain toward the nose. Blinking keeps spreading this tiny wet coat while you look at the world.

About this explanation

Starting knowledge: Know where the eyelids are.

Sources

  • National Eye Institute — How Tears Work
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