Aging and the shrinking pupil (1 Viewer)

[MacGee]

Birdwatching.com has an article about how your pupil shrinks with age, so that (in daylight) a 20-year old's pupil will be 4.7mm, while a 60-year old's will be 3.1mm. What implications does this have for my choice of binoculars? I'm rapidly approaching 60, and have artificial lenses in my eyes (does this have any effect on anything?). I've been looking at binoculars in the 8x30/8x32 range to use in the daytime - hardly ever in the twilight. If my pupils are around 3.1mm, then I should theoretically only need an 8x25 for daytime use, but I'm still tending towards the 8x30ish for the sake of a bit more leeway in eye placement. Is this reasonable, or have I got the wrong end of the stick - or the wrong stick entirely?

Michael.

 

[ceasar]

In using our eyes, more available light for the pupil won't hurt anything in normal daily use, and in fact might be advantageous. I'm older than you and I have 2 artificial lens implants. I routinely use either a Nikon 8 x 30 EII or a Leica 7 x 42 BN Trinovid as my binocular of choice. In twilight, overcast or rainy conditions the Leica is my choice and the difference in brightness over the Nikon is quite apparent. I would never use a binocular with an exit pupil of under 3.5 as my 1st choice under any condition. I don't know how wide my pupils open under dark conditions but I can see the difference in brightness between the 2 binoculars and I have no problem placing my pupils in the right alignment with their exit pupils. The same thing goes when I use the 7 x42's under very bright conditions. No problems at all there either. BTW, I was nearsighted before my cataract surgerys and as far as I'm concerned the results of the surgerys were miraculous!
Bob

 

[Milt DuCharme]

I am 57 and use a Nikon SE 8x32 for bird watching. It provides plenty of light into twilight.

 

[Tero]

Look at it this way: the extra brightness will never be harmful or lose anything in the view, provided you do not have an eye condition that prefers less bright light.

BUT, if FOV is most important to you, then use that as a criterion in picking one.

 

[Alexis Powell]

Although it is true that there is a very strong effect of age on pupil diameter, it is also true that there is TREMENDOUS individual variation in pupil diameter at a given age. If you are really interested in making a purchasing decision that is influenced by pupil diameter considerations, you need to measure your own pupil diameter. Your personal pupils may not be anywhere close to the population mean for your age.
--AP

 

[henry link]

Michael,

I'm 58. I tried an experiment today to measure my pupil size under different lighting conditions. I used a small dentist's mirror held about 6" in front of my eye with a large magnifying glass between the mirror and my eye to make measurements easier. The tiny mirror blocked an insignificant percentage of the light reaching my eye. I held a millimeter ruler as close to the pupil as possible.

I found that 2mm is the very smallest my pupil will close to. That was looking at an uncomfortably bright halogen light and looking up at a bright partly cloudy sky. Moving into a shaded area caused my pupil to open to 4mm and looking into a dark area underneath heavy shrubbery (with the sun now behind clouds) caused my eye to open to about 5mm. I'll do more measurements at twilight and add them to the above. The Porters' article failed to make the distinction between how quickly the pupil responds to changes in light levels, which only takes a few seconds, and the much longer period required for the buildup of the protein rhodopsin in the rods of the retina for complete dark adaptation.

Henry

Twilight measurements were 4mm for "bright twilight" (5 minutes after sunset standing in an open area with clear sky above) and 5mm in the same spot 20 minutes after sunset. In darker shaded areas I could see the pupil was open to about 5.5mm before the light became too dim for accurate measurement. I suspect with binocular eyecups blocking most of the side and sky light all of these measurements would be a bit larger. The biggest surprise was the 5mm opening from looking into a very dark shaded area in the middle the afternoon. That condition probably happens quite often in woodland birding particularly on a cloudy day.

 

[MacGee]

Thank you for all these replies. I've found them both interesting and enlightening.

Michael.

 

[elkcub]

Just to reinforce Henry's observations, it may be helpful to read this article: http://amateurastronomy.org/EH/Apr96.PDF#search="age and pupil size". In particular, see the table on pg. 8.

The table posted by the Porters is questionable in my opinion. I'm also rather curious how max. (or resting?) pupil diameter was measured for daylight conditions. But the dark adapted PD for older folks is inconsistent with other data in the literature.

Ed

 

[Touty]

Just to reinforce Henry's observations, it may be helpful to read this article: http://amateurastronomy.org/EH/Apr96.PDF#search="age and pupil size". In particular, see the table on pg. 8.

The table posted by the Porters is questionable in my opinion. I'm also rather curious how max. (or resting?) pupil diameter was measured for daylight conditions. But the dark adapted PD for older folks is inconsistent with other data in the literature. Ed

This whole thread is fascinating. I was reading a book in a local bookshop that said glasses were the cause of short-sightedness and setting out exercises to do for the accommodation muscles and iris, saying it was a lack of forced accommodation (near focus to distant objects and exposure to harsh bright light and trying to do stuff in low light) that meant that people today need glasses. I'm 45 and still OK as regards close focus (about 20cm) but I have noticed that the bulb wattage is climbing (pupil dia.?). I wonder if atropine drops would keep the iris through exercising them to the maximum dilation?

 

[AlanFrench]

Oyster's "The Human Eye: Structure and Function" includes a graph of Pupil Diameter as a Function of Age. The description says, in part, "At any age, the pupil diameter in the population varies by about 4mm."

Pupil size increases from birth to about age 15, after which it slowly decreases as we age. At age 15 the median is 7mm, but it varies from 5mm to 9mm. At 30 the median is around 6.3mm, at 40 it is about 5.9mm, at 50, 5.3; 60, 5.0; 70, 4.7; and 80, 4.3. All these have a variation in the population of +/- 2mm.

Unfortunately, visual acuity also declines with age, and that may be more detrimental than changes in our maximum pupil opening (eyes generally work better with smaller pupils).

Clear skies, Alan

 

[Keith Dickinson]

This whole thread is fascinating. I was reading a book in a local bookshop that said glasses were the cause of short-sightedness and setting out exercises to do for the accommodation muscles and iris, saying it was a lack of forced accommodation (near focus to distant objects and exposure to harsh bright light and trying to do stuff in low light) that meant that people today need glasses. I'm 45 and still OK as regards close focus (about 20cm) but I have noticed that the bulb wattage is climbing (pupil dia.?). I wonder if atropine drops would keep the iris through exercising them to the maximum dilation?

Don't mess with atropine drops....prolonged use can cause glaucoma, by causing the pressure within your eyeball to rise. Perfectly safe as a dilator for use during an eye examination every 6 months or so but not regularly.

 

[AlanFrench]

[SNIP] I'm 45 and still OK as regards close focus (about 20cm) but I have noticed that the bulb wattage is climbing (pupil dia.?). I wonder if atropine drops would keep the iris through exercising them to the maximum dilation?

That's pretty typical. I wouldn't mess with atrophine drops, for the reasons Keith pointed out, and because the visual acuity of the wide open pupil is pretty horrid. The next time you visit the eye doctor, and he dialates your pupil, try reading something. I tried my 7x42 binoculars after one of my eye doctor visits, and I simply couldn't get anything I would have called focused.

Clear skies, Alan

 

[ceasar]

Alan,
I remember coming home on an early September summer evening, after an eye exam, with my eyes fully dilated. I went out on my deck and sat down to watch the stars come out. The first one to show itself was what I thought was the planet Venus, shining as bright as I have ever seen it. But, curiously, it was in the wrong place? I looked at it for about a minute or so when I realized that it wasn't Venus after all, but the star Arcturus and it was indeed the brightest I have ever seen it! It looked to be about -4 magnitude! I had a great 1/2 hour of 1X seeing until the Atropine started wearing off.
Cheers,

Bob

 

[AlanFrench]

Alan,
I remember coming home on an early September summer evening, after an eye exam, with my eyes fully dilated. I went out on my deck and sat down to watch the stars come out. The first one to show itself was what I thought was the planet Venus, shining as bright as I have ever seen it. But, curiously, it was in the wrong place? I looked at it for about a minute or so when I realized that it wasn't Venus after all, but the star Arcturus and it was indeed the brightest I have ever seen it! It looked to be about -4 magnitude! I had a great 1/2 hour of 1X seeing until the Atropine started wearing off.
Cheers,

Bob

Bob,

I'll have to time my next appointment late in the afternoon.

What did Arcturus look like?

Clear skies, Alan

 

[Tero]

And guys, don't drive too fast after an eye exam, I tried it once. I could see and drive, but mostly back roads.

 

[Curtis Croulet]

Unfortunately, visual acuity also declines with age, and that may be more detrimental than changes in our maximum pupil opening (eyes generally work better with smaller pupils).

Clear skies, Alan

I'm 61, and I cannot, for example, split Epsilon Lyrae with my naked eye, which was easy when I was young, and I cannot see as faintly, either. The Horsehead Nebula, which I could detect in my 8-inch reflector in a very dark sky as recently as 15 years ago, is now impossible even in my 10-inch scope. An H-beta filter doesn't help much. There's a certain spurious 3-D effect in the summer Milky Way that I haven't been able to see for years, although that may simply be due to the inevitable increase in light pollution.

 

[elkcub]

...
Unfortunately, visual acuity also declines with age, and that may be more detrimental than changes in our maximum pupil opening (eyes generally work better with smaller pupils).

Clear skies, Alan

Alan,

Here is an ancient article that's relevant to your speculation, at least for rod vision AND dependent on the apparatus used. It was written in the longest year of my life, 1943, when I was seven years old.

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1393467

By accident I also found the possible source of the Porter's data. It seems to be litigation oriented and of questionable validity. Designed to sensationalize, I'd say.

http://www.visualexpert.com/Resources/olderdrivers.html

Ed

 

[AlanFrench]

And guys, don't drive too fast after an eye exam, I tried it once. I could see and drive, but mostly back roads.

I had an eye exam once on a nice, sunny early spring day - with about 3 inches of freshly fallen snow on the ground. I had to sit in my car and let the drops wear off some before I could drive.

Clear skies, Alan

 

[ceasar]

Bob,

I'll have to time my next appointment late in the afternoon.

What did Arcturus look like?

Clear skies, Alan

Alan,
It's been at least 9 or 10 years since this incident and memory is elusive but I will never forget how bright Arcturus was, even against a still partially light sky. Minus 4 is rather an exaggeration, but I will state categorically that it was as bright as Jupiter to my eyes. At least minus 2.5. Much, much brighter than it's normal minus 1. Curiously, I don't recall it being yellow, which is the color I normally associate with it. It was brilliant blue-white. It was the first star out that night and I watched it and the stars of the Summer Triangle come out over the next 1/2 hour or so. They also seemed much more brilliant than normal. After another 1/2 hour or so went by my eye's pupils receded to normal.

As you know, there is still an window of opportunity for the next month or so for you to test this phenomenon yourself on Arcturus. (Weather permitting, of course.) If you get a chance to do it, PM me. I didn't plan mine, it was a fluke occurence. I don't recall what time my clinic closed so I can't even give you an educated guess on what time to have your eyes dilated. :h?:

Cordially,
Bob

 

[hinnark]

This figure comfirms: pupil size is related to age and the variation is high indeed:

http://homepages.uni-tuebingen.de/martin.adler/pup_age.html

For me this means that everybody has to find out his own pupil diameter.

Steve