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Of course, I think I can safely assume if an eye is left pointing directly towards sun for a long period of time it does get major damage. However, staring at the sun also hurts very quickly. That pain seems like a very natural* defense mechanism against eye damage.

Also, I guess technically even a very quick glance at the sun does cause temporary eye damage, as there is a visible distortion spot in sight for a short while afterwards.

So the question is: Is possible for someone to naturally stare at the sun for an amount of time required for significant permanent eye damage, or whether the pain will become too much significantly sooner than any such damage would happen?

Then: If not, is it possible with simple willpower, without special training or medication, to force oneself to ignore the pain for a long enough time to cause such damage?

Also: Is there a difference in this between adults, children and babies?

And as a bonus, are there any special environmental situations where this does not apply? For example: sunset, sunrise, solar eclipse, major fog, underwater, or light filtered through something else.

* - Natural is here not in the sense of "everything natural is good", but in the sense of "it is reasonable to assume there would be an evolutive advantage from it".

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I once had a patient (I work at mental health and addiction institutions) that stared at the sun purposedly, trying to become temporarily blind - he thought it would not last - in order to be released from the institution. The poor fellow had both his eyes marked with a permanet spot near the center. Luckily, he did it one eye at a time (no irony here), so the spots were not centered, meaning he could still see the center of images. I know, it is anecdotal, but still... –  user523 Mar 12 '11 at 16:55
    
Well, having done it as a kid, and having an opthalmologist say "there's been an insult", I think the answer's probably Yes. Didn't you ever burn holes in paper with a magnifying glass? It's the same idea. –  Mike Dunlavey Mar 14 '11 at 20:07
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Why don't you try it? Be sure to report your findings! –  muntoo May 20 '11 at 3:07
    
I use to stare sun for a long time in my childhood, still at 23 my eye sight is perfect. Should i conclude that children can stare it safely? –  LifeH2O Jun 14 '11 at 14:56
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@LifeH2O No, you should conclude that it is possible to not get serious, permanent eye damage from staring at the sun. –  Ilari Kajaste Jun 14 '11 at 16:15

2 Answers 2

up vote 42 down vote accepted

An ordinary person can easily stare at the sun or a solar eclipse long enough to cause significant, possibly permanent loss of vision.

Looking directly at the sun for even brief periods of time may cause blindness or severe damage to the eye. Solar retinopathy, damage to the eye’s retina due to solar radiation, and blindness to varying degrees and persistence frequently result from sungazing during a solar eclipse. Although vision loss due to this damage is generally reversible, permanent damage and loss of vision have been reported. Most eye care professionals advise patients to avoid looking directly at the sun. Exposure to ultraviolet radiation, produced by the sun, is associated with damage to the eye, including pterygium and cataracts.

(Sungazing)

Phil Plait recently cited an ‘‘unprecedented rise in the number of cases of solar retinopathy’’ directly linked to a popular Irish shrine where people stared at the sun in order to experience ‘‘visions of the Virgin Mary’’.

(Plait)

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So, that's a "yes" then. Thanks for the good answer! –  Ilari Kajaste Mar 16 '11 at 9:51
    
Regarding natural defense: this is probably similar to burns in that once you feel it, you are already burned. –  horatio May 3 '11 at 14:16
    
As a kid I was challenging myself how much I can stare into the sun without blinking and I never hand any eyesight problems. –  Alexandru May 4 '11 at 17:21
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@Alexandru Nice anecdote that in theory could point towards invalidating this answer. However, the question - and this answer - is not about how long you can stare without blinking, but whether it's possible to stare long enough to cause harm, blinking or not. –  Ilari Kajaste May 23 '11 at 5:29
    
@horatio actually your retina cant' feel pain, so the "pain" from looking at bright things is probably all psychological. –  Ben Brocka Nov 16 '12 at 20:59

The amount of light emitted by the solar corona is far too little to do damage. So during a total eclipse, but only during totality, it is completely safe to look at the corona with naked eyes. NASA is a good source of information about eclipses, including safe viewing and photography techniques. According to the NASA Eye Safety page:

The Sun can be viewed safely with the naked eye only during the few brief seconds or minutes of a total solar eclipse. Partial eclipses, annular eclipses, and the partial phases of total eclipses are never safe to watch without taking special precautions. Even when 99% of the Sun's surface is obscured during the partial phases of a total eclipse, the remaining photospheric crescent is intensely bright and cannot be viewed safely without eye protection [Chou, 1981; Marsh, 1982]. Do not attempt to observe the partial or annular phases of any eclipse with the naked eye. Failure to use appropriate filtration may result in permanent eye damage or blindness!

So it would be a good idea, especially if the eclipse is not near local sunrise or sunset, to be aware of how long totality is expected to last, and be ready to look away as soon as you glimpse the "diamond ring" effect where the disk of the sun first becomes visible through a notch on the moon's limb.

Photography of the eclipse with a DSLR requires that you look through the camera. If the mirror were locked up, then the camera would be projecting a nearly in focus image of the sun onto the shutter curtain, and eventually onto the film or sensor. Clearly, significant damage to your eye and/or the camera is possible. To avoid damage, a solar filter should be used in front of the lens. NASA also has a good resource page related to eclipse photography.

During the 2006 eclipse I was very close to the center of the path of totality on a yacht in the Mediterranean, attempting photography with a hand-held DSLR with a 500mm lens. I had a Thousand Oaks Optical black polymer solar filter on the front of the lens, and it was fun to see the disk of the sun with decent magnification. However with that filter in place, the whole frame was dead black when pointed anywhere in the sky that didn't include the sun. Aiming was a bear. While practicing, I made the mistake of opening my other eye to check the larger view which was not a pleasant experience.

For use aboard ship, I punched one eye out of a cardboard pair of eclipse watching glasses that happened to be made with the same filter material I had on the lens. With the camera on the unfiltered eye, and the other eye filtered I was able to successfully aim and photograph the partial phase without further pain or injury.

During totality, I removed the filter and shot the corona with the same lens.

Partial Phase and Sunspots Corona at Totality

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Please reference you claim appropriately. –  Ebenezer Sklivvze May 3 '11 at 7:13
    
@Sklivvz, I've added a bunch of links to supporting material from NASA about eclipse viewing. –  RBerteig May 4 '11 at 0:57
    
Why the heck didn't you just leave both eyes in? I took photos of the 1999 solar eclipse in Romania wearing eclipse-watching glasses with both eyes in. Through the camera you can still see where the eclipse is with the glasses on. –  Kyralessa May 4 '11 at 1:00
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Because the camera is a DSLR, and the filter on the front of the telephoto lens effectively renders it safe to look through for one eye. The other eye was a seriously painful mistake to open in that position. A second layer of the filter behind the camera would likely have made the viewfinder too dim to be useful, but that is an assumption I have not actually tested. Knocking an eye out of the filter+paper glasses was a quick and dirty solution that worked, so I didn't try much harder. Not using a filter on the open eye was accidentally tested, and found painful. –  RBerteig May 4 '11 at 1:08
    
Much better, thanks! –  Ebenezer Sklivvze May 4 '11 at 6:51

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