Any eye docs out there? Safety of midriasis agents?

A friend of mine has asked occasionally whether dilating eyedrops,
such as used for ophthalmic exams, could be used to artificially
dilate the pupil and improve night vision. Other than completely
eliminating ability to focus closer than infinity, (almost all the
agents I have seen also paralyze the ciliary muscles, and make it
impossible to focus) I was wondering about the safety of such a
technique. This would also wreak havoc with trying to read star
charts, and possibly using fixed-focus finderscopes, and possibly
telrads. I believe the image we are looking at is located at the focal
plane, usually within the eyepiece, so close focus by the eye is
needed. This may not be a show stopper, since people continue to use
scopes after cataract surgery, so I assume one would simply have to
use the focuser to bring the image into sharp focus. However, I do
know that many agents that dilate the pupil also risk increasing
intraocular pressure, which in fact could be quite dangerous.

Am I missing something else here? Could people with low intraocular
pressure gain a few mm of extra pupil size (better living through
chemistry)? Or would risk (acute glaucomatous change, visual
blurring, or other unmentioned risks) prevent use of these agents?
I'm enough of a coward to not risk it, but I'm sure someone has tried
it, and ophthamologists or optometrists could probably answer this
question quickly and possibly definitively. Since I don't work in
those fields, I don't have the answers up my sleeve, but I'd be
interested in the information.

Clear skies (and big pupils)

John F.

"John A. Flamini" wrote:

A friend of mine has asked occasionally whether dilating eyedrops,
such as used for ophthalmic exams, could be used to artificially
dilate the pupil and improve night vision. Other than completely
eliminating ability to focus closer than infinity, (almost all the
agents I have seen also paralyze the ciliary muscles, and make it
impossible to focus) I was wondering about the safety of such a
technique. This would also wreak havoc with trying to read star
charts, and possibly using fixed-focus finderscopes, and possibly
telrads. I believe the image we are looking at is located at the focal
plane, usually within the eyepiece, so close focus by the eye is
needed. This may not be a show stopper, since people continue to use
scopes after cataract surgery, so I assume one would simply have to
use the focuser to bring the image into sharp focus. However, I do
know that many agents that dilate the pupil also risk increasing
intraocular pressure, which in fact could be quite dangerous.

Am I missing something else here? Could people with low intraocular
pressure gain a few mm of extra pupil size (better living through
chemistry)? Or would risk (acute glaucomatous change, visual
blurring, or other unmentioned risks) prevent use of these agents?
I'm enough of a coward to not risk it, but I'm sure someone has tried
it, and ophthamologists or optometrists could probably answer this
question quickly and possibly definitively. Since I don't work in
those fields, I don't have the answers up my sleeve, but I'd be
interested in the information.


Having been on the receiving end of a long term study of the application
of atropine as an anti-myopic, I can reasonably say that that particular
agent doesn't have any apparent glaucomatous effects, at least from what
I've heard. OTOH, opthamologists stopped applying it because it simply
wasn't efficaceous for that particular problem.

*BUT*, and here's the big but, your accomodation goes right down the
dumper for one and second and even more important, dilating the pupil
that far makes the eye use parts of the optical system that are, to put
it politely, quite aberrated. In short, you may pick up a little bit in
terms of light gathering ability but it'll much more than be wiped out
by the poor quality of your vision while using a dilating agent.
--
Mike
http://www.concentric.net/~richmann/

If aperture matters for the telescope, I would imagine that it would
also matter for the eye as well. A 7 mm pupil could admit almost twice
as much light as a 5 mm pupil(6.25pi vs 12.25pi sq mm). These
differences are minimized at the eyepiece except if you have a
scope/ep combo with a large exit pupil, but no one does purely scope
viewing. I often spend a considerable time gazing naked (OK, with
glasses) eye both to enjoy and locate the next object, which I then
line up with a Telrad. A few extra mm at the pupil would probably
allow me to see dimmer stars, if the view did not suffer from
excessive aberration, as I suspect it would if the pupil were
artificially enlarged.

Your comments about night vision being more a retinal phenomenon are
well taken, and I agree fully. Preservation of night vision by using
red lights, and the dimmest ones possible at that, are more important
throughout the night than 1 or 2 extra mm of pupil, but I think a
larger pupil would help for viewing the night naked eye, which is a
big part of my enjoyment. At age 49, I don't have too many options.

Thanks for the comments.

John F.

John A. Flamini wrote:
A friend of mine has asked occasionally whether dilating eyedrops,
such as used for ophthalmic exams, could be used to artificially
dilate the pupil and improve night vision. Other than completely
....snip...

I think night vision is related more to the retina adapting than the size
of the pupil. Pupil size only comes into play if the exit pupil of the
eyepiece is larger than the pupil of the eye (i.e. very low
magnification). Of course, it might have a small affect on naked eye
night vision "IF" it dilates the pupil a little more than would occur
naturally. If not, then the only possible advantage would be to speed up
the dilation and maintain it after exposure to light. Based on all that,
why even take the chance that repeated use might be damaging? Eye patches
are cheap and the effect is easily reversible (just take it off!).

Bryan

On 11 Jul 2003 06:17:41 -0700, (John A. Flamini) wrote:

If aperture matters for the telescope, I would imagine that it would
also matter for the eye as well.

It does, if observing naked eye or at very low magnifications. All the same,
there are so many other things going on with age: decreased retinal response,
increased corneal absorption, increased scatter in the lens and vitreous, etc
that the benefits of simply increasing the pupillary diameter a bit might be
fairly small. And even though you receive less light through a smaller pupil,
you also have considerably more acute vision: far less spherical aberration,
chromatic aberration, and astigmatism.

BTW, it is not the ability of the pupil to dilate that decreases with age, but
the actual size of the pupil. In other words, the pupil is smaller both in light
and dark conditions.

A 7 mm pupil could admit almost twice
as much light as a 5 mm pupil(6.25pi vs 12.25pi sq mm).

Mydriatics tend to be less effective on older eyes, so you still might not get
as large a pupil as you'd like. It is common when performing surgical procedures
on older patients to have difficulty achieving sufficient mydriasis.

Anyway, all mydriatic agents are potent drugs, with significant systemic side
effects. When you administer eye drops, 90% or more of the agent is washed into
your sinuses where it is readily absorbed into the bloodstream, where
cardiovascular and neurologic effects are seen. While serious complications are
uncommon, I still don't think these are the sort of things you want to be using
regularly!

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

John A. Flamini wrote:
A friend of mine has asked occasionally whether dilating eyedrops,
such as used for ophthalmic exams, could be used to artificially
dilate the pupil and improve night vision. Other than completely
eliminating ability to focus closer than infinity, (almost all the
agents I have seen also paralyze the ciliary muscles, and make it
impossible to focus) I was wondering about the safety of such a
technique. This would also wreak havoc with trying to read star
charts, and possibly using fixed-focus finderscopes, and possibly
telrads. I believe the image we are looking at is located at the focal
plane, usually within the eyepiece, so close focus by the eye is
needed. This may not be a show stopper, since people continue to use
scopes after cataract surgery, so I assume one would simply have to
use the focuser to bring the image into sharp focus. However, I do
know that many agents that dilate the pupil also risk increasing
intraocular pressure, which in fact could be quite dangerous.

From a discussion with my late opthalmologist, it's likely not
worth it risk or not. Most dark adaptation is chemical rather
than in pupil size, apparently, so the gain in using such a chemical
approach isn't all that great anyway.

Bill Keel

Please don't get me wrong. I am arguing against the use of these
medications, and I was speaking in my last post about the throughput
of light through pupils of different sizes only. I suspected that
aberrations in the aging eye would not allow for a better view, but if
all else was equal, that an increase in pupillary size would be
beneficial. I have not tried nor do I advocate the use of these
medications, and I agree with your warnings at the end of your post.
I have seen patients with delerium and syncope from use of several eye
medications which were only administered "topically", yet had systemic
effects.

John F.

In article ,
John A. Flamini wrote:

Please don't get me wrong. I am arguing against the use of these
medications, and I was speaking in my last post about the throughput
of light through pupils of different sizes only. I suspected that
aberrations in the aging eye would not allow for a better view, but if
all else was equal, that an increase in pupillary size would be
beneficial. I have not tried nor do I advocate the use of these
medications, and I agree with your warnings at the end of your post.
I have seen patients with delerium and syncope from use of several eye
medications which were only administered "topically", yet had systemic
effects.

I'm forced to take such medications from time to time, due to
inflammations in the iris, which I get once every few years or so.
No-one knows the cause. It only happens in one eye at a time though,
so you'll have normal vision in the other eye -- which indeed helps.
:-)

Anyway, I can tell you that your focus will be different than "at
infinity" (or whatever your normal "rest focus" is), so you'd need to
get special eyeglasses for that situation, adapted to the abnormal
focus of your eyes when you take such medication.

So I believe anyone taking medications to make their pupils large so
they can see fainter stars will get disappointed at the results:
you'll get a better naked-eye view of the skies without that.

OTOH there's no long-term danger to your vision from those
medications. Your vision will be lousy for up to a week, and you'll
be sensitive to daylight (sunglasses in daytime is a must!) since
a full daylight scene with fully open pupils is a bit too much for
the retina. But after that week, your vision will be back to normal.

--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://www.stjarnhimlen.se/
http://home.tiscali.se/pausch/