Measuring Dark Pupil

Here's what I did:

1) Stand in front of mirror with measuring stick and get a read on the
outside diameter of my iris.
2) Take a picture of my eye in a darkened room using the digital camera set
to basic flash mode (no double flashing for light sense. Didn't worry too
much about focus, and took a couple pictures at varying distances to get a
usable focused image.)
3) Transfer image to laptop via USB.
4) Display image and hold measuring stick to displayed image of eye, iris
and pupil.
5) Measure the diameter of the iris in the picture.
6) Measure the diameter of the pupil in the picture.
7) Calculate the percentage of pupil occupying the iris, by diameter.
8) Multiply the mirror and measuring stick value by percentage derived in
step 7.

Result:
Iris diameter = 13mm
"Dark" pupil diameter by percentage = 50%
Dark pupil diameter = 6.5mm

I'm 44 years old.

-Stephen Paul

Here's what I did.

Photocopied the star image dot scale from my Sky Atlas 2000.0

Cut the copy with an exacto knife right down the center of the dots
that represent the different magnitudes. Measured the dots.

Stood in front of the mirror with my dot scale held up in front of my
eye (overlapping my pupil by one half) and slid the scale back and
forth until one of the half dots matched my pupil. I measured 5.5mmL
and 6mmR.

I was not able to do this in any light less than a subdued daylit room
light. In a fairly darkened room I could not see my pupils. In a
fully darkened room with a red light I could not see my pupils.
Turning even a low room light on I could see my pupils instantly
contract.

So last time (a few weeks ago) I visited the eye doctor I asked him to
measure my dark adapted pupils. He uses a similar half dot scale.
Only thing is he could not do it in a fully darkedned room. At first
in a fully dark room with a finger over his tiny light he got
7.5-8.0mm, but he stated he was having a hard time really seeing the
pupil accurately. He also needed to use a subdued light. With a dim
room light turned on behind me, he measured 6.5mmL and 7.0mmR.

My attempt at home was in a room far more lit that at the eye doctor's
office.

I'm near 51.

edz

I use a set of metric Allen wrenches. Go out at night and wait for your=20
eyes to be fully dark adapted. At least 20 minutes. Hold an Allen wrench =

one at a time close to your eye and look at a medium bright star. I rest =

the wrench on my cheek. With small sizes you will see two stars, one on=20
each side of the wrench. Work up until you only see one star, on one=20
side of the wrench or the other. I've heard some people can see two=20
stars when using a regular wooden pencil. That's about 7mm. To me a=20
pencil looks like a board! I can just see two stars with a 3mm wrench=20
and only see one with a 4mm thus my pupil is right around 4mm. Sky &=20
Telescope magazine sells a little gauge for measuring nighttime pupils=20
as well. It's a piece of mylar with paired holes from 1mm to 9mm apart.=20
It works on the same principal as my Allen wrench method. You can also=20
use strips of black paper cut to various widths or drill bits.

-Florian
Stargazing.com

On Wed, 22 Oct 2003 23:52:32 -0400, "Stephen Paul"
wrote:

Here's what I did:

1) Stand in front of mirror with measuring stick and get a read on the
outside diameter of my iris.
2) Take a picture of my eye in a darkened room using the digital camera set
SNIP...
I'm 44 years old.

-Stephen Paul


I tried a different method - probably not very accurate, though. I
cut a strip of paper about 8 inches long and tapered it from about 7mm
to about 3mm. Then I marked off the points at which the strip was
3,4,5,6 and 7mm wide.

Several times during an observing session last Friday, I held the
strip up to my observing eye and looked at Mars. When I moved the
strip up or down to the point where Mars blinked out, I pinched the
strip at the position in front of my eye and then looked at the strip
to see where I was marking it. The index marks indicated how wide the
strip was at that point.

The best I did was about 5.5mm but we had a pretty bright sky and
other stuff I was doing that prevented my getting fully dark-adapted.
I plan to try the same method at a really dark site to see how much,
if any, difference there is there.

Les Blalock
http://www.txastro.com

"edz" wrote in message
om...
Here's what I did.

Photocopied the star image dot scale from my Sky Atlas 2000.0

Cut the copy with an exacto knife right down the center of the dots
that represent the different magnitudes. Measured the dots.

Stood in front of the mirror with my dot scale held up in front of my
eye (overlapping my pupil by one half) and slid the scale back and
forth until one of the half dots matched my pupil. I measured 5.5mmL
and 6mmR.

I was not able to do this in any light less than a subdued daylit room
light. In a fairly darkened room I could not see my pupils. In a
fully darkened room with a red light I could not see my pupils.
Turning even a low room light on I could see my pupils instantly
contract.

So last time (a few weeks ago) I visited the eye doctor I asked him to
measure my dark adapted pupils. He uses a similar half dot scale.
Only thing is he could not do it in a fully darkedned room. At first
in a fully dark room with a finger over his tiny light he got
7.5-8.0mm, but he stated he was having a hard time really seeing the
pupil accurately. He also needed to use a subdued light. With a dim
room light turned on behind me, he measured 6.5mmL and 7.0mmR.

My attempt at home was in a room far more lit that at the eye doctor's
office.

I'm near 51.

edz

http://astro.umsystem.edu/atm/ARCHIV.../msg00354.html


Dave

In article ,
"Stephen Paul" wrote:

Here's what I did:

1) Stand in front of mirror with measuring stick and get a read on the
outside diameter of my iris.
2) Take a picture of my eye in a darkened room using the digital camera set
to basic flash mode (no double flashing for light sense. Didn't worry too
much about focus, and took a couple pictures at varying distances to get a
usable focused image.)
3) Transfer image to laptop via USB.
4) Display image and hold measuring stick to displayed image of eye, iris
and pupil.
5) Measure the diameter of the iris in the picture.
6) Measure the diameter of the pupil in the picture.
7) Calculate the percentage of pupil occupying the iris, by diameter.
8) Multiply the mirror and measuring stick value by percentage derived in
step 7.

Result:
Iris diameter = 13mm
"Dark" pupil diameter by percentage = 50%
Dark pupil diameter = 6.5mm

I'm 44 years old.

-Stephen Paul



I used a metric ruler in a dark bathroom with a dim red light to see by.
I just held it up to my eye after my eyes had dark-adapted and I could
see the ruler. My measurement also came to 6.5mm (I am 43 yrs old).

However, I soon after went to the eye doctor and he dilated my pupils
with that icky stuff they put in your eyes and told me my pupils only
dilated to 5.5mm. But I have to admit, I don't trust any measurement
they did in a lighted room after dumping stuff in my eye.

I'm sticking with 6.5mm until I measure it differently.

-sdg

On Wed, 22 Oct 2003 23:52:32 -0400, "Stephen Paul"
wrote:

Here's what I did:

1) Stand in front of mirror with measuring stick and get a read on the
outside diameter of my iris.
2) Take a picture of my eye in a darkened room using the digital camera set
to basic flash mode (no double flashing for light sense. Didn't worry too
much about focus, and took a couple pictures at varying distances to get a
usable focused image.)
3) Transfer image to laptop via USB.
4) Display image and hold measuring stick to displayed image of eye, iris
and pupil.
5) Measure the diameter of the iris in the picture.
6) Measure the diameter of the pupil in the picture.
7) Calculate the percentage of pupil occupying the iris, by diameter.
8) Multiply the mirror and measuring stick value by percentage derived in
step 7.

Result:
Iris diameter = 13mm
"Dark" pupil diameter by percentage = 50%
Dark pupil diameter = 6.5mm

I'm 44 years old.

-Stephen Paul

I performed this operation twice, for accuracy...

I just sat in the bathroom, in the dark, but only for two or
three minutes before I stood up to the mirror with red light and
6-inch rule with metric graduations in hand...

My iris is closer to 14mm in diameter.

My pupils, in both eyes, easily reached 7mm, and perhaps even
approaching 8mm.

This is not surprising to me, given the stark, almost iris-eclipsing
diameters in an elementary-school picture, and having been
mistakenly suspected by a teacher of being under the influence
of marijuana in the 11th grade(marijuana dilates the pupils
considerably.)

Not that I didn't indulge altogether in reckless youth, however.

I am 39.

Alan

"Alan W. Craft" wrote in message
...

I just sat in the bathroom, in the dark, but only for two or
three minutes before I stood up to the mirror with red light and
6-inch rule with metric graduations in hand...

My iris is closer to 14mm in diameter.

My pupils, in both eyes, easily reached 7mm, and perhaps even
approaching 8mm.

Cool!! I'm beginning to wonder how accurate is the statement that 5mm is
typical for the over 40 crowd. Maybe we are doing this all wrong.

-Stephen

Cool!! I'm beginning to wonder how accurate is the statement that 5mm =
is
typical for the over 40 crowd. Maybe we are doing this all wrong.


Mine are less than 4mm. ;-( But my active imagination makes up for it!

-Florian

On Fri, 24 Oct 2003 14:20:24 -0700, "Florian" wrote:

Cool!! I'm beginning to wonder how accurate is the statement that 5mm is
typical for the over 40 crowd. Maybe we are doing this all wrong.


Mine are less than 4mm. ;-( But my active imagination makes up for it!

-Florian

You're not as old as that would seem to suggest.

I wonder what accounts for it.

Perhaps you nearly exhausted the associated muscles over time
by some unknown activity or other.

Alan