# Eyelids vs x-rays **URL:** \ **Category:** Factual Questions\ **Created:** [August 5, 2013, 11:10pm UTC](https://boards.straightdope.com/t/eyelids-vs-x-rays/665445 "2013-08-05T23:10:04Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![Apollon](https://avatars.discourse-cdn.com/v4/letter/a/e47774/32.png) [@Apollon](https://boards.straightdope.com/u/Apollon)\ **Post date:** [August 5, 2013, 11:10pm UTC](https://boards.straightdope.com/t/eyelids-vs-x-rays/665445/1 "2013-08-05T23:10:04Z")
My dentist took a panoramic x-ray of my teeth the other day. After dressing me in that lead apron and squeezing my head inside the machine, she told me to close my eyes and to keep them closed until the x-ray is done. Why would she say such a thing? If the rays had the potential to damage the eyes, would the eyelids really serve as an effective barrier? I somehow doubt that. Is my dentist crazy, or is there something to it? ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [August 5, 2013, 11:28pm UTC](https://boards.straightdope.com/t/eyelids-vs-x-rays/665445/2 "2013-08-05T23:28:42Z")
Just a WAG, but perhaps so you don’t flinch as the machine moves around your head. ---
**Author:** ![dracoi](https://avatars.discourse-cdn.com/v4/letter/d/90db22/32.png) [@dracoi](https://boards.straightdope.com/u/dracoi)\ **Post date:** [August 5, 2013, 11:47pm UTC](https://boards.straightdope.com/t/eyelids-vs-x-rays/665445/3 "2013-08-05T23:47:06Z")
Closing your eyes would also make you less tempted to turn your head to look at something in the background. ---
**Author:** ![Ethilrist](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ethilrist/32/4604_2.png) [@Ethilrist](https://boards.straightdope.com/u/Ethilrist)\ **Post date:** [August 6, 2013, 1:15am UTC](https://boards.straightdope.com/t/eyelids-vs-x-rays/665445/4 "2013-08-06T01:15:13Z")
Also, the process of blinking might inspire you to twitch enough to throw off the scan. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [August 6, 2013, 1:17am UTC](https://boards.straightdope.com/t/eyelids-vs-x-rays/665445/5 "2013-08-06T01:17:56Z")
The dentist or technician was wrong not to tell you the reason. ---
**Author:** ![TurboNuke](https://avatars.discourse-cdn.com/v4/letter/t/f19dbf/32.png) [@TurboNuke](https://boards.straightdope.com/u/TurboNuke)\ **Post date:** [August 6, 2013, 2:29am UTC](https://boards.straightdope.com/t/eyelids-vs-x-rays/665445/6 "2013-08-06T02:29:09Z")
Eyelids would protect against alpha and beta radiation not x-rays though. Maybe the dentist is confused about the radiation coming from the machine? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 6, 2013, 2:36am UTC](https://boards.straightdope.com/t/eyelids-vs-x-rays/665445/7 "2013-08-06T02:36:42Z")
There are very few sources of radiation that produce one and only one kind. It’s quite plausible that the X-ray machine might also produce significant ultraviolet (or maybe even visible), which would damage your eyes but which would be blocked (or at least, significantly mitigated) by your eyelids. ---
**Author:** ![Isilder](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@Isilder](https://boards.straightdope.com/u/Isilder)\ **Post date:** [August 6, 2013, 2:42am UTC](https://boards.straightdope.com/t/eyelids-vs-x-rays/665445/8 "2013-08-06T02:42:18Z")
Its a false implication that closing the eyes was for radiation safety. Its just to keep him safe from mechanical injury, or dust, or strong light, and to keep the head still (reflex ,etc). Some people pass out from a sudden annoyance to the eye. So the injury could me to other parts of his body, not his eye ! just caused from having the eye insulted. Someone I know did pass out when getting the puff of air test pressure for Glaucoma. (I don’t think he had any illness, being his colleague at work in a small office for more than a year… ) If he passes out, he could fall over and get fall injuries, so its wise to close the eyes. Some people have seizures/fits/epilepsy/etc triggered by bright flashing lights… ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [August 6, 2013, 3:28am UTC](https://boards.straightdope.com/t/eyelids-vs-x-rays/665445/9 "2013-08-06T03:28:24Z")
> [@Chronos](#): > > It’s quite plausible that the X-ray machine might also produce significant ultraviolet (or maybe even visible)… As far as I know, most X-ray tubes have beryllium windows. No visible light or UV is going to penetrate that. And considering how easy it is to block visible light & UV while transmitting X-rays (beryllium isn’t the only way, most low-Z elements would work), it would be highly irresponsible for a medical equipment manufacturer to not take such measures. ---
**Author:** ![dstarfire](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dstarfire/32/5762_2.png) [@dstarfire](https://boards.straightdope.com/u/dstarfire)\ **Post date:** [August 6, 2013, 5:22am UTC](https://boards.straightdope.com/t/eyelids-vs-x-rays/665445/10 "2013-08-06T05:22:48Z")
As others have said, it’s to keep you from blinking or flinching (even a tiny bit). As that thing moves into your field of vision, only inches from your face, most people will either flinch or clench their eyes (I clench), blurring what’s already a small and finely detailed picture. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 6, 2013, 9:48pm UTC](https://boards.straightdope.com/t/eyelids-vs-x-rays/665445/11 "2013-08-06T21:48:27Z")
Hm, good point, **scr4**. I guess shielding would be a lot easier at the source. ---
**Author:** ![Pasta](https://avatars.discourse-cdn.com/v4/letter/p/ecccb3/32.png) [@Pasta](https://boards.straightdope.com/u/Pasta)\ **Post date:** [August 6, 2013, 10:03pm UTC](https://boards.straightdope.com/t/eyelids-vs-x-rays/665445/12 "2013-08-06T22:03:59Z")
I had one of these scans a few years back, and the dentist said explicitly that I should close my eyes so that I don’t involuntarily track the machine, etc.