Age and the ability to see in the dark

Started by Tom Bourg, 11/20/2005 01:21PM
Posted 11/20/2005 01:21PM | Edited 11/21/2005 11:37PM Opening Post
Hello,

Last night I was at the observatory and a few of my students showed up to get extra points.(I teach Earth Science, Environmental Science, and Physical Science in high school).

Anyway, the sky wasn't very clear and with the excessive sky glow I needed averted vision to see the pleides. Three of my ninth graders, who don't know the difference between astronomy and astrology, looked up and asked me if those six stars that were very obvious to them were the big dipper. They could see the stars clearly.

This got me thinking about how much visual acuity I have lost in my 58 years. It has to be very significant. I wonder if anyone has estimates or can direct me to articles about the subject.

I know I have trouble splitting some double stars that were easy when I was a teenager and obviously I've lost a magnitude or so in seeing dim stars. I wonder if anyone has done research into this.

Thanks guys. I really like this site.

Tom B.
Posted 11/20/2005 01:37PM #1
Tom Bourg said:
[SNIP]
This got me thinking about how much visual acuity I have lost in my 58 years. It has to be very significant. I wonder if anyone has estimates or can direct me to articles about the subject.

I know I have trouble splitting some double stars that were easy when I was a teenager and obviously I've lost a magnitude or so in seeing dim stars. I wonder if anyone has done research into this.

Thanks guys. I really like this sight.

Tom B.

Tom,

If you can locate a copy - I found one through inter-library loan - look at Clyde W. Oyster's "The Human Eye (Structure and Function)." It has a chapter called Time and Change that talks about the effects of aging on vision. He also provides references for further reading.

Your maximum pupil size changes with age. According to Oyster, "After an initial increase in pupil size from birth to about age 15, pupil size decreases slowly with advancing age. The mean pupil diamter decreases by about 0.4 mm/decade after age 15." He also notes that at any age the pupil diameter varies by about 4mm across the population (a number the suprised me).

The graph of visual acuity with age shows a decline starting about 50, with the rate of decline increasing with age.

Clear skies, and wishing for younger eyes, Alan

Posted 11/20/2005 10:00PM #2
While this won't answer your question concerning how much acuity you have lost this article answers some questions as to how vision works. I thought it was interesting because I fiddle around with image intensified technology.
http://www.narcap.org/TheEyeandNightVision.htm
Harry
Posted 11/21/2005 10:29PM #3
William Green said:

What do you mean by "visual acuity"?
[SNIP]
Bill

The ability to see fine detail.

To quote Oyster - "Even after refractive errors have been corrected, visual acuity begins to deline slowly in the mid-50s, then declines more rapidly with increasing age." Later he writes "Much of the decline of visual acuity with age can be attributed to transmission losses in the eye's optical media."

It is worth getting this book out of a library, if only to read the chapters on Ocular Geometry and Topography and on Time and Change.

People tend to leave the eye out of the observing equation. Even a healthy eye has considerable influence on the view with large exit pupils and large eye pupils.

Clear skies, Alan
Posted 11/21/2005 10:42PM #4
Hello Bill,

Probably all of the above compared to when I was a teenager.

This happens all the time at the observatory, btw. Us old guys are always talking about how much better the youngsters eyes are compared to ours and how good our eyesight was when we were younger..

I remember last year a buddy and I were using one of the observatories Meade 10" gps units on Jupiter. The four Jovians were visibla and we could just barely make out a dim star next to jupiter. A kid about 10 looked through the eyepiece and casually said that he saw five moons. He could see the star very easily.

I understand that if one can't focus to a point the light of the stars will appear spread out and thereby dimmer I also know that maximum pupil diameter also decreases, but I suspect more is working than that.

I didn't need glasses until I was in my mid-forties and my eyesight corrects to 20/20 but the kids can see better than all of us old guys. I think I can say that and no one will disagree with me.This weekend when I go I am going to take a poll and see for sure. wink

Good luck and clear skies.

Tom B.