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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. |
#2
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Any eye docs out there? Safety of midriasis agents?
"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/ |
#3
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Any eye docs out there? Safety of midriasis agents?
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. |
#4
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Any eye docs out there? Safety of midriasis agents?
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 |
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Any eye docs out there? Safety of midriasis agents?
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 |
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Any eye docs out there? Safety of midriasis agents?
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. |
#8
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Any eye docs out there? Safety of midriasis agents?
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/ |
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