# Why is a solar eclipse more harmful to your eyes? **URL:** \ **Category:** Factual Questions\ **Created:** [August 14, 2017, 6:21pm UTC](https://boards.straightdope.com/t/why-is-a-solar-eclipse-more-harmful-to-your-eyes/793653 "2017-08-14T18:21:45Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![ReticulatingSplines](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@ReticulatingSplines](https://boards.straightdope.com/u/ReticulatingSplines)\ **Post date:** [August 14, 2017, 6:21pm UTC](https://boards.straightdope.com/t/why-is-a-solar-eclipse-more-harmful-to-your-eyes/793653/1 "2017-08-14T18:21:45Z")
So I’ve been wondering this for years, and I still can’t find a single source that actually explains why looking at a partial solar eclipse is so dangerous compared to looking at the non-eclipsed sun. Initially I figured that maybe they think that people are more likely to stare at the sun during an eclipse, and that’s where the added risk comes from, but a lot of news stories have lines like this: “[‘Even just momentarily looking at eclipse can cause solar burns on the retina,’ said Dr. Greg Hill, optometrist with Avera Medical Group Eye Care.](http://www.ksfy.com/content/news/Avera-Medical-Minute-AMcK-How-to-view-the-solar-eclipse-safely-439727023.html)” I’ve momentarily looked at the sun many, many times during my life and my retinas are fine. Is the eclipsed sun more dangerous than regular sun or not? ---
**Author:** ![x-ray\_vision](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/x-ray_vision/32/351_2.png) [@x-ray\_vision](https://boards.straightdope.com/u/x-ray_vision)\ **Post date:** [August 14, 2017, 6:33pm UTC](https://boards.straightdope.com/t/why-is-a-solar-eclipse-more-harmful-to-your-eyes/793653/2 "2017-08-14T18:33:27Z")
> [@ReticulatingSplines](#): > > Initially I figured that maybe they think that people are more likely to stare at the sun during an eclipse, and that’s where the added risk comes from I think that’s basically the answer, but also what exactly we’re fixated on. It’s probably easier to fixate on the black part, while the retinas are being damaged by what’s remaining of the sun. I found this: > [@](#): > > A momentary glance, such as we do occasionally on a sunny day, does indeed focus a very intense image of the sun on the transparent neural tissue at the back of the eye, the retina, and a highly absorbent layer just beyond, but we have a reflex to avert our eye and the heat buildup is brief and little damage results. If one closes the eye after such a chance event, one will note a series of bright ‘after images’ of the sun staggered irregularly, indicating the eye’s protective motion during the glance. Since there is nothing novel to see, a simple disk, no specific fixation results. > > … > > I am always asked why the partial eclipse is so special a hazard, since most days we can safely glance at the sun without care. The danger comes from the fact an eclipse changes the circular, too bright disk, into something interesting. The brightness is the same and still too great, but in eclipse there is a shape, a black part, and the crescent remaining of the sun. Now the normal safety feature of eye motion is defeated by the cognitive event of having a point to fixate. The two sharp cusps are points that the eye may focus upon and now the damaging image on the retina is stopped on the most sensitive neural tissue. This short stoppage begins damage from all mechanisms, too much blue light, too much UV, and too much heat. This damage is not recoverable. [http://web.williams.edu/Astronomy/IAU\_eclipses/look\_eclipse.html](http://web.williams.edu/Astronomy/IAU_eclipses/look_eclipse.html) > [@](#): > > but a lot of news stories have lines like this: > > “[‘Even just momentarily looking at eclipse can cause solar burns on the retina,’ said Dr. Greg Hill, optometrist with Avera Medical Group Eye Care.](http://www.ksfy.com/content/news/Avera-Medical-Minute-AMcK-How-to-view-the-solar-eclipse-safely-439727023.html)” > > I’ve momentarily looked at the sun many, many times during my life and my retinas are fine. One person’s “momentarily” can be a little longer than another’s. ---
**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 14, 2017, 6:48pm UTC](https://boards.straightdope.com/t/why-is-a-solar-eclipse-more-harmful-to-your-eyes/793653/3 "2017-08-14T18:48:08Z")
And those momentary glances at the Sun have done damage to your eyes. Not much, and most of it probably recovered, but still some. The cumulative effect of all of those momentary glances is one of the reasons why eyesight degrades with age. ---
**Author:** ![ReticulatingSplines](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@ReticulatingSplines](https://boards.straightdope.com/u/ReticulatingSplines)\ **Post date:** [August 14, 2017, 6:54pm UTC](https://boards.straightdope.com/t/why-is-a-solar-eclipse-more-harmful-to-your-eyes/793653/4 "2017-08-14T18:54:03Z")
Ah, thank you. Your Google-fu is stronger than mine. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [August 14, 2017, 7:04pm UTC](https://boards.straightdope.com/t/why-is-a-solar-eclipse-more-harmful-to-your-eyes/793653/5 "2017-08-14T19:04:44Z")
We’ll be wanting our eyes in their best condition for the two minutes of totality … seeing the partial phases ain’t worth the risk of missing the Main Show … and during totality eye protection is not necessary … and that’s **only during totality** … ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [August 14, 2017, 7:36pm UTC](https://boards.straightdope.com/t/why-is-a-solar-eclipse-more-harmful-to-your-eyes/793653/6 "2017-08-14T19:36:34Z")
> [@watchwolf49](#): > > We’ll be wanting our eyes in their best condition for the two minutes of totality … seeing the partial phases ain’t worth the risk of missing the Main Show … and during totality eye protection is not necessary … and that’s **only during totality** … But the wise individual does not take off the eye protection lest he misjudges the moment when they are needed again. ---
**Author:** ![I\_Love\_Me\_Vol.I](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/i_love_me_vol.i/32/521_2.png) [@I\_Love\_Me\_Vol.I](https://boards.straightdope.com/u/I_Love_Me_Vol.I)\ **Post date:** [August 14, 2017, 7:55pm UTC](https://boards.straightdope.com/t/why-is-a-solar-eclipse-more-harmful-to-your-eyes/793653/7 "2017-08-14T19:55:15Z")
> [@John\_Mace](#): > > But the wise individual does not take off the eye protection lest he misjudges the moment when they are needed again. The wise and extra cautious individual. However, with the Interwebz available to all and sundry nowadays it is possible to know the exact times of totality at the exact location you are viewing from. With a good watch and taking great care one can watch totality with the naked eye and have the goggles safely back on once totality ends. This is a link to a to map where I think you can check those times but it looks like the server is overloaded now so I couldn’t check (but I’ve seen it before). On the subject of that guy’s map page… he created an overlay to Google maps that gives all kinds of info about the eclipse. But as we get closer to the event, his server is likely to get swamped–as it is right now, I think. Why hasn’t Google themselves created a map like this? Or have they? I mean… Google makes goofy interactive Doodles for National Chipmunk Secretary’s Day… surely they would make a nice interactive map for a once-in-a-lifetime eclipse, wouldn’t they? ---
**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 14, 2017, 7:57pm UTC](https://boards.straightdope.com/t/why-is-a-solar-eclipse-more-harmful-to-your-eyes/793653/8 "2017-08-14T19:57:39Z")
The wise individual might put on his glasses ten or fifteen seconds earlier than needed, just to be sure, but if you leave them on for the entire totality period, you’ll be missing one heck of a show. ---
**Author:** ![standingwave](https://avatars.discourse-cdn.com/v4/letter/s/9de0a6/32.png) [@standingwave](https://boards.straightdope.com/u/standingwave)\ **Post date:** [August 14, 2017, 11:56pm UTC](https://boards.straightdope.com/t/why-is-a-solar-eclipse-more-harmful-to-your-eyes/793653/9 "2017-08-14T23:56:10Z")
> [@I\_Love\_Me\_Vol.I](#): > > The wise and extra cautious individual. > > However, with the Interwebz available to all and sundry nowadays it is possible to know the exact times of totality at the exact location you are viewing from. With a good watch and taking great care one can watch totality with the naked eye and have the goggles safely back on once totality ends. > > [This](http://www.eclipse2017.org/xavier_redirect.htm) is a link to a to map where I think you can check those times but it looks like the server is overloaded now so I couldn’t check (but I’ve seen it before). > > On the subject of that guy’s map page… he created an overlay to Google maps that gives all kinds of info about the eclipse. But as we get closer to the event, his server is likely to get swamped–as it is right now, I think. Why hasn’t Google themselves created a map like this? Or have they? > > I mean… Google makes goofy interactive Doodles for National Chipmunk Secretary’s Day… surely they would make a nice interactive map for a once-in-a-lifetime eclipse, wouldn’t they? Better to download an app such as \*\* solar eclipse timer\*\* that provides a audible countdown and knows your location by GPS… [![](https://img.youtube.com/vi/qc7MfcKF1-s/maxresdefault.jpg "HOW TO WATCH THE ECLIPSE (AND SHADOW SNAKES) - Smarter Every Day 171") ](https://www.youtube.com/watch?v=qc7MfcKF1-s)