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When we are awake, blinking helps distribute the tears so the cornea and the entire conjunctiva are wet and moist. But how is this maintained during the night, when we are sleep and there is no blinking. Doesn't the tear just pool down? Or is there some sort of tone in the palpebral muscle of the eyelids.

Mhkhm
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    With the eyelid closed, what would cause the eye surface to dry out? – Bryan Krause Apr 22 '20 at 22:29
  • tears would be sucked by gravity into the nasolacrimal duct. So the tears aren't distributed throughout the eye surface, that's what I am saying. – Mhkhm Apr 22 '20 at 22:46
  • Welcome to SE.Biology! You might find it helpful to look at this guide for asking a question that's more likely to get a good answer: https://biology.stackexchange.com/help/how-to-ask. Can you identify a specific source or a quote on eye wetting that is leading you to confusion? You might also consider posting this question on SE Medical Sciences where people are more familiar with human physiology. – Maximilian Press Apr 23 '20 at 04:02

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The tear system supplies your eye with moisture and lubrication while you sleep:

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Also, your eyes move when you sleep, so that probably helps redistribute the moisture.

  • What about Bell's Phenomenon? If the eye does move at night, how many times does it do this? Is it enough for even distribution of the tear throughout the outer surface? – Mhkhm Apr 22 '20 at 22:46
  • Tear production is decreased at night. – Mhkhm Apr 22 '20 at 22:47
  • @Mhkhm one stage of sleep is even named Rapid Eye Movement. – John Apr 23 '20 at 01:09
  • @Mhkhm you probably don't need as much tears, since your eyes are closed, and there is less evaporation. –  Apr 23 '20 at 05:06