In the run-up to the Great American Eclipse of 2017, numerous outlets advised would-be sun watchers of the dangers of staring directly at the sun, even when most of it was blotted out during the eclipse’s peak. However, this message may not have reached everyone, and authentic eclipse glasses were so difficult to find in the last few days before the celestial event that some people may have simply gone without.
So, how would someone tell if the eclipse damaged their eyesight? And what should you do if you feel you have damaged your vision?
According to Ralph Chou, a professor emeritus of optometry and vision science at the University of Waterloo, in Ontario, Canada, it may be difficult to tell whether the sun has caused damage (at least at first). NPR interviewed Chou, who had this to say:
It takes at least 12 hours before we can tell if anything has happened. The thing is, if people just saw the sun briefly without a protective filter — just a fraction of a second — the chances they’ve hurt themselves are very low.
If they looked at the display of a camera or a smartphone but didn’t look through the optics at the sun, they’re in no danger. While it may look bright, it isn’t all that bright by comparison. They were not getting direct optical radiation from the sun in that case. It’s just a duplicate of whatever the sensors see, and there’s no danger in that.
If, for some reason, they forgot to use their filters entirely — well, [permanent damage is] always a possibility, but I would hope that after all the publicity, that that didn’t happen.
Chou said that some of the symptoms of eclipse-damaged vision would include blurred vision and “spots” in vision: “The very center of the vision might have a spot, or multiple spots, that were missing in their vision — that were very, very blurred. Around it, there might be some clear spots. It really depends on exactly what happened, and what kind of injury there is at the back of the eye.”
USA Today also interviewed a number of eye specialists on the topic. Ohio optometrist Michael Schecter told USA Today that, “the moon’s covering makes it a lot less painful to look at it for a lot longer. That makes it tempting for folks to peer over their cardboard eclipse glasses to see ‘what’s really going on.'”
According to USA Today, Jacob Chung, Chief of Ophthalmology at New Jersey’s Englewood Hospital, echoed Chou’s statements by saying that very brief exposure won’t harm someone, but any longer than that is dangerous. He said, “If you look at it for a second or two, nothing will happen. Five seconds, I’m not sure, but 10 seconds is probably too long, and 20 seconds is definitely too long.”
If you feel you are experiencing persistent blurred vision, as Chou describes, see an optometrist. Chou advises that will be easier than getting in to see an ophthalmologist; if the optometrist can tell that there is damage then they can refer the person to an ophthalmologist for further help.