The Solar Eclipse and Eye Health

>The Solar Eclipse and Eye Health

The Solar Eclipse and Eye Health

By | 2018-03-24T09:14:47-07:00 August 8, 2017|

My radio ads direct you to this site concerning the eclipse and eye health. My comments concerning the upcoming eclipse are about viewing it in and around Pullman, Washington. Those viewing elsewhere should get their information from experts within those areas. You can find good information at these sites: NASA (the best), Excellent Map, Harvard edu. I do not agree with everything in all these sites, but their advice is sound.

The NASA site finishes with this statement:

“A student who heeds warnings from teachers and other authorities not to view the eclipse because of the danger to vision, and learns later that other students did see it safely, may feel cheated out of the experience. Having now learned that the authority figure was wrong on one occasion, how is this student going to react when other health-related advice about drugs, alcohol, AIDS, or smoking is given

[Pasachoff, 1997] Misinformation may be just as bad, if not worse than no information at all.”

This is an interesting argument. It may be a lame argument. The authority figures who counsel on alcohol, drugs, and sex recommend restraint and/or abstinence because the misjudgments of youth surrounding these vices prove harmful to a small percentage. We all made poor judgments about some perilous or grievous aspect of life in our youth and most of us came out okay. 

NASA seems unconcerned about the reputations of the authority figures who are actually wrong about the vast majority who suffer no consequences concerning youthful misjudgments, but they are greatly concerned about the reputations of the authorities trying to prevent the vision damage that will occur to an errant minority who will view the upcoming solar eclipse. It all seems a little contrived.

The latter site ends with this:

“It is my greatest disappointment that so many have missed seeing one of nature’s most beautiful events – a total solar eclipse – because of misinformation. No photograph, no TV or other laboratory technique can represent or capture this unique physical phenomenon. The colors and contrast, the detail and structure of the image is beyond reproduction.”

This author seems to have lived a sheltered life if his “greatest disappointment” is those who missed a perfect view of a solar eclipse.  Personally, my greatest disappointment is my poor representation of humanity to my parents, wife, children and the rest of humanity; or maybe our failures in the Middle East, our insistence that everything controversial must be run through the Supreme Court, etc. 

First, you must understand that as an eye doctor I have had to deal with those who have viewed the overhead sun for excessive amounts of time. Some of these individuals were children. I’ll take that back. The majority were children who received life-long solar damage – never to see normally again. This is a different perspective than these scientists who are so concerned one might be “deprived” of a less than optimal view of a solar eclipse.

I will continue to err on the side of caution. If one of my patients has a damaged retina because of my advice that patient’s life will never be the same and it will haunt me and my reputation forever. If one of my patients is deprived of a slightly less than optimal view of the upcoming eclipse, well so be it. Their lives will be little changed – and so will my conscience and integrity.

There are those who argue, “Well, I look at the sun all the time during sunrises and sunsets, so what’s the big deal about looking at a solar eclipse. It can’t be any brighter.”

The answer is that a midday viewing of the upcoming eclipse will be overhead viewing sunlight energy approaching earth’s atmosphere at nearly 90 degrees.

On the horizon, the sunlight energy approaches at an oblique angle. The angle of incidence on the earth determines the amount of solar energy per unit of surface area. The mathematics are complex. Lambert’s Law (1760’s) was named after Johann Heinrich Lambert, a French Huguenot who spent way too much of his life hunched over a desk figuring out the loss of energy with oblique angle light when he could have been hunting, fishing, courting or enjoying a fine wine. 

Now this does not take into account that viewing the sun overhead places only about two miles between you and raw unfiltered sunlight. While viewing the sun on the horizon is totally different.  You are not seeing the true sun at all. You see a refracted rendition of the sun, with the short wavelengths (blue, violet and ultraviolet) scattered so badly they are nearly out of the equation. What you see is a red image or a yellow one at minimum after the sun energy has passed through the equivalent of 120 miles of dense atmosphere – not just two miles.

A hundred years or so after Lambert arrived at his oblique light equation another mathematician, this time a German, August Beer, forsook a lot of cold ones to wade through equations and derive Beer’s Law which calculates the loss of light energy as it passes through atmospheric gases. It was combined with Lambert’s Law, so we now have the Lambert-Beer Law.

But, after you run light through the Lambert-Beer Law you also must calculate loss of energy from water vapor, dust, smoke, cow flatus, and other air contaminants. What I call the WvDSCf equation. I would call it the David Law, but I’m having a little trouble with the Cf constant, so it’s just not complete yet.

I think now you might be getting an idea of how much more filtration there is on a rising or setting sun as compared to the overhead sun. Still I wouldn’t sit and stare at a sunset for seven minutes either – Moderation-in-all-Things Law.

At this point I’m not saying you should not view the eclipse on August 21st in and around Pullman, Washington during the 2017 solar eclipse, but you should be using all the precautions available, and err on the side of caution. Again, the NASA site provides excellent guidelines.

 

Photo credit: By Manoj.dayyala (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons