# Perception of light "rays"

**URL:** <https://boards.straightdope.com/t/perception-of-light-rays/217359>\
**Category:** Factual Questions\
**Created:** [December 6, 2003, 10:39am UTC](https://boards.straightdope.com/t/perception-of-light-rays/217359 "2003-12-06T10:39:15Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![II\_Gyan\_II](https://avatars.discourse-cdn.com/v4/letter/i/bbe5ce/32.png) [@II\_Gyan\_II](https://boards.straightdope.com/u/II_Gyan_II)\
**Post date:** [December 6, 2003, 10:39am UTC](https://boards.straightdope.com/t/perception-of-light-rays/217359/1 "2003-12-06T10:39:15Z")

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When I squeeze my eyes tight, I can see light “rays” emanate from light sources like bulbs or LEDs. What’s this phenomenon and why does it occur?

[sub]P.S. I’m bespectacled, but it occurs unaided as well.[/sub]

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**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\
**Post date:** [December 6, 2003, 1:56pm UTC](https://boards.straightdope.com/t/perception-of-light-rays/217359/2 "2003-12-06T13:56:57Z")

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I’m guessing a combination of diffraction and refraction. When you squeeze your lids up to the point right before they close, I’d imagine the thin layer of “eye juice” that keeps the surface of your eye moist starts to distort, thereby causing defraction and refraction of the lightrays that in turn hit your retna.

but this is just a WAG.

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**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\
**Post date:** [December 6, 2003, 1:58pm UTC](https://boards.straightdope.com/t/perception-of-light-rays/217359/3 "2003-12-06T13:58:27Z")

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Also, diffraction from the eyelids and eyelashes too.

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**Author:** ![aerodave](https://avatars.discourse-cdn.com/v4/letter/a/f08c70/32.png) [@aerodave](https://boards.straightdope.com/u/aerodave)\
**Post date:** [December 6, 2003, 5:58pm UTC](https://boards.straightdope.com/t/perception-of-light-rays/217359/4 "2003-12-06T17:58:25Z")

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Nothing to add…but I found the phrase “eye juice” to be funnier than it ought to be.

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**Author:** ![billy](https://avatars.discourse-cdn.com/v4/letter/b/ecd19e/32.png) [@billy](https://boards.straightdope.com/u/billy)\
**Post date:** [December 6, 2003, 10:11pm UTC](https://boards.straightdope.com/t/perception-of-light-rays/217359/5 "2003-12-06T22:11:37Z")

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I’m with kevsnyde, it’s diffraction from the eyelashes.

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**Author:** ![bbeaty](https://avatars.discourse-cdn.com/v4/letter/b/c0e974/32.png) [@bbeaty](https://boards.straightdope.com/u/bbeaty)\
**Post date:** [December 7, 2003, 9:03am UTC](https://boards.straightdope.com/t/perception-of-light-rays/217359/6 "2003-12-07T09:03:06Z")

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What happens if you shave off your eyelashes and try squinting again? (Notice I said _your_ eyelashes. As in, “not mine.”)