I've noticed that if I don't sleep for a long time, my eyes get dry, and no amount of moisture helps to moisturize them. I moisturize every 10 minutes and it doesn't help. The answer is sleep. Our body needs to sleep for about 8 hours, so that our eyes can function properly again.

But what happens during sleep that helps the eyes work without dryness after we wake up for several hours? Are there any research papers explaining that? I'm very interested in learning about this.

Thank you!


1 Answer 1


Tears are very complex fluids. Their job is to lubricate, moisturize, and oxygenate the corneas and inner eyelids, to be antibiotic/antiviral, to break down byproducts, etc. They're continually produced and their composition changes with environmental demands (e.g., they're more acidic at the end of the night, there are more of some types of enzymes).

When your eyes are tired, you blink less, and so you bathe your eyes much less frequently in natural tears. Thus your eyelids and corneas have more of the chemicals in tears that weren't washed away and replaced.

What about artificial tears? Or plain water?

  • not continually replenished
  • likely your eyes aren't moisturized/oxygenated/lubricated nearly as well
  • because even artificial tears are very different chemically

If you want to learn more, here's a pretty readable chapter looking at what happens in a similar "adverse" situation -- while wearing contact lenses:

Environmental Conditions and Tear Chemistry Leo Carney


National Research Council (US) Working Group on Contact Lens Use Under Adverse Conditions; Ebert Flattau P, editor. Washington (DC): National Academies Press (US); 1991.


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