# Darkness to brightness: Eye damage **URL:** \ **Category:** Factual Questions\ **Created:** [May 28, 2016, 8:59am UTC](https://boards.straightdope.com/t/darkness-to-brightness-eye-damage/755882 "2016-05-28T08:59:02Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Velocity](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/velocity/32/18006_2.png) [@Velocity](https://boards.straightdope.com/u/Velocity)\ **Post date:** [May 28, 2016, 8:59am UTC](https://boards.straightdope.com/t/darkness-to-brightness-eye-damage/755882/1 "2016-05-28T08:59:02Z")
If someone went from several hours pitch darkness to sudden exposure to brightness, would it cause eye damage by degrading the rod/cone light receptors? ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [May 28, 2016, 9:21am UTC](https://boards.straightdope.com/t/darkness-to-brightness-eye-damage/755882/2 "2016-05-28T09:21:08Z")
It won’t cause permanent damage (as long as we’re talking about a reasonable amount of bright light here), but it will ruin your night vision for a bit. It takes the rods and cones a while to become sensitive to low light levels. The cones recover from brightness fairly quickly. The rods take a lot longer to recover though, something like 20 minutes to half an hour or so. Cones don’t function all that well in dim light even at their best, so the rods are much more important to your ability to see in low light conditions than the cones are. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [May 29, 2016, 3:45am UTC](https://boards.straightdope.com/t/darkness-to-brightness-eye-damage/755882/3 "2016-05-29T03:45:36Z")
Remember that Chilean mine collapse in August 2010, in which 33 miners were trapped deep in a mine for 69 days before they were rescued? Those miners were required to wear dark glasses when they were brought up, to protect their eyes from the light. And some of these miners were brought up at night, and still were required to wear those glasses. (I’m not sure how long they had to wear them, although I’m pretty sure some article I read at the time did discuss it.) ---
**Author:** ![Velocity](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/velocity/32/18006_2.png) [@Velocity](https://boards.straightdope.com/u/Velocity)\ **Post date:** [May 29, 2016, 4:43am UTC](https://boards.straightdope.com/t/darkness-to-brightness-eye-damage/755882/4 "2016-05-29T04:43:05Z")
> [@Senegoid](#): > > Remember that Chilean mine collapse in August 2010, in which 33 miners were trapped deep in a mine for 69 days before they were rescued? > > Those miners were required to wear dark glasses when they were brought up, to protect their eyes from the light. And some of these miners were brought up at night, and still were required to wear those glasses. (I’m not sure how long they had to wear them, although I’m pretty sure some article I read at the time did discuss it.) What would have happened without the shades? Damaged retinas? ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [May 29, 2016, 5:57am UTC](https://boards.straightdope.com/t/darkness-to-brightness-eye-damage/755882/5 "2016-05-29T05:57:39Z")
I’ve heard that if you are exposed to darkness for an extended period that your pupils become dilated, and after some time the eye muscles get so relaxed that they can’t quickly react to light and you risk retina damage if you go from say a cave or a mine into direct sunlight. I used to go caving when I was a lot younger (and a lot thinner) and a lot of people told me that if you are ever trapped in a cave for an extended period to turn on your flashlight for a short time every few hours to prevent this from happening. That said, I’m not certain how true it actually is. It certainly takes longer than “several hours”, otherwise we’d all go blind from sleeping in darkness all night then waking up to the morning sun. Does it take a few days of complete darkness? I dunno. A google search on those miners finds some people who were skeptical about the sunglasses that they were given, saying that it was more of an advertising gimmick than an actual medical need. Those were $450 sunglasses, not some ZZ top style cheapies. ---
**Author:** ![buddha\_david](https://avatars.discourse-cdn.com/v4/letter/b/ee7513/32.png) [@buddha\_david](https://boards.straightdope.com/u/buddha_david)\ **Post date:** [May 29, 2016, 6:02am UTC](https://boards.straightdope.com/t/darkness-to-brightness-eye-damage/755882/6 "2016-05-29T06:02:23Z")
Not to mention the obvious solution: if the light’s too bright, just shut your eyes. ---
**Author:** ![jtur88](https://avatars.discourse-cdn.com/v4/letter/j/e9c0ed/32.png) [@jtur88](https://boards.straightdope.com/u/jtur88)\ **Post date:** [May 30, 2016, 2:28am UTC](https://boards.straightdope.com/t/darkness-to-brightness-eye-damage/755882/7 "2016-05-30T02:28:49Z")
Don’t watch the Eclipse You eyes can be permanently damaged by direct exposure to extreme brightness, such as the solar disc. ---
**Author:** ![Velocity](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/velocity/32/18006_2.png) [@Velocity](https://boards.straightdope.com/u/Velocity)\ **Post date:** [May 30, 2016, 3:14am UTC](https://boards.straightdope.com/t/darkness-to-brightness-eye-damage/755882/8 "2016-05-30T03:14:02Z")
> [@jtur88](#): > > Don’t watch the Eclipse You eyes can be permanently damaged by direct exposure to extreme brightness, such as the solar disc. This is not what this thread is about at all.