Iris dilating eye drops?

[Stargazer51N]

I recently accompanied a relative to have their eyes examined at an eye hospital. They had drops put in their eyes that caused their iris to open so the doctor could get a better view inside the eye. I was astonished at the size the iris opened (~10mm diameter, leaving only a 1mm band around it). The effect lasted about 4 hours.

Got me thinking .....

A) how on earth do the drops work?

would they be any good for astronomy? (I'm not serious about this one as it clearly would not be good for your eyes )

Anyway, it was a bit freaky ...made them look like an alien of some sort

[Photosbykev]

No idea how they work but I used to have the same drops in my eyes during a annual laser user eye test and had to wear sunglasses for a few hours afterwards. The last couple of years they have put drops into my eyes after the test that returns the eyes back to normal very quickly.

[johninderby]

Had that done a few weeks ago. Didn't bother me at all afterwards. Did make me wonder though if I should have had an evening appointment and then gone straight home to get in some observing.

John

[umadog]

The drops probably contain a drug known as atropine, which dilates the pupils. It works by activating acetylcholine receptors that cause the muscles in your iris to contract.

It won't help much with astronomy because, interestingly, pupil dilation is a relatively insignificant part of dark-adaptation. I can think of three pieces of evidence for this:

1. Pupil size changes in seconds, but dark adaptation takes many minutes.

2. The dynamic range of your visual system is around 10 orders of magnitude, give or take. The pupil's area changes in size from about 8 mm to about 1 mm (those are extremes) 8^2/1^2=64. So a dilated pupil only lets in 64 times more light than a contracted pupil. Being generous and calling that 2 orders magnitude means that we still have 8 orders or magnitude in dark adaptation which needs explanation.

3. You can still see lots of stuff through a telescope with a 2mm or 3mm eyepiece exit pupil. That's the same thing as your actual pupil diameter being those sizes. Sure, stuff looks a little dimmer but not that much dimmer: it's still detectable. So even if you dilated your pupils to 10 mm, it wouldn't be noticeable at the eyepiece unless you have an eyepiece exit pupil that is at least the same size as your dilated pupils. The only place it may help a bit is naked-eye observing.

So what is dark adaptation? Most of dark adaptation takes place in the retina. Many things happen there: Your rods, which are effectively disconnected from the optic nerve during daylight, now wire themselves up. The level of photopigment in the rods gradually increases over a period of many minutes. The period over which photoreceptors average photons also increases. If those processes didn't take place, you'd be blind at night.

So what's the pupil for? The pupil's main role is contract in bright conditions to provide a sharp image. This hides optical flaws in your cornea and lens. A dilated pupil in bright conditions leads to blurry views. In the dark, your acuity is bad anyway and you're desperate for photons. So you dilate your pupil to take advantage what light there is. When I desperate, I really do mean it. It's possible to read newspaper headlines in starlight under a non-light polluted sky (I've tried it, it's true). Under those conditions (reading from the page), each rod receives 1 photon every 10 minutes (!). So every photon counts!

[Mr Spock]

'Visual purple' (Rhodopsin), a biological pigment of the retina, is what allows us to see in the dark. It is blanked out by light and takes about 30 minutes to regenerate which is why we need dark adaptation.

[Quatermass]

i get iritus and have the drops for it but its horrible and makes your eyes ach rather have my eyes normal.

Sent from my GT-S5670 using Tapatalk

[karlyboo]

ive had these drops too and can say with experience that the other side effect can be fuzzy halo's around lights and blured vission...doc told me not to drive for a few hours until side effects settle...(cant drive anyway)....not sure how it effects everyone but some side effects would hinder you even more perhaps.......also.......suppose drops did work...eyes are very precious to us and very delicate... what long term damage drops could do if you used it regulary ?.... ....i do my wieghts without steriods thankies so i pass on that one

[661-pete]

Yes I had atropine put in my eyes for my first-ever eye test, as a small child (1950s). I didn't know the practice was still in use. Not a pleasant experience at all. I remember having to go to school the following day, my pupils were still dilated and I was virtually blinded by the daylight. The effect took about 24 hours to wear off.

Remember: atropine is derived from the main toxic constituent of deadly nightshade (Atropa belladonna)!

Avoid!

[syd_malicious]

The drops probably contain a drug known as atropine, which dilates the pupils. It works by activating acetylcholine receptors that cause the muscles in your iris to contract.

counts!

Close but no cigar.

The eye has an accommodation reflex (which means that when you look at something closely the pupil contracts) as well as contracting in bright light.

The atropine does bind to muscarinic acetylcholine receptors but this blocks rather than stimulates the muscle. So atropine prevents contraction of the pupil (by either of the above mechanisms) rather than directly causing dilatation. As it also paralyzes the ciliary muscles you cannot then focus.

However it's unlikely to have been atropine as this takes days to wear off so was probably something like tropicamide.

[661-pete]

However it's unlikely to have been atropine as this takes days to wear off ...

Yes this sounds consistent with my experience: I said '24 hours' but it may have been longer. I suppose, half a century ago, they didn't have alternatives.

I recall that I became quite distressed in class at school (well, who wouldn't?), so much so that the head teacher was sent for and I was allowed to sit in her study (with curtains drawn) for the rest of the day, and my parents were notified. Possibly (not sure about this) the optician had put in the atropine without advising my mother of the consequences, and my mother gave the optician something of an ear-bashing in return. At any rate, I was not blamed for any of this.

Ah well - it was all a long time ago.

[x6gas]

Remember: atropine is derived from the main toxic constituent of deadly nightshade (Atropa belladonna)!

Avoid!

And some more trivia: belladonna translates to "beautiful lady" and this name comes from the practice of women putting it in their eyes to dialate their pupils in order to appear more attractive.

That or it blurred their vision making their suitors appear more attractive to them!

[Stargazer51N]

Thanks to all for the detailed answers, very interesting.

[ixalon]

Does make one wonder if a drug could be formulated that did speed up dark-adaptation? I guess not (at least safely) or defence/military agencies would already have developed and be using it.

[661-pete]

Does make one wonder if a drug could be formulated that did speed up dark-adaptation? I guess not (at least safely) or defence/military agencies would already have developed and be using it.

I suppose another approach would be to try to replicate the tapetum lucidum which exists in many nocturnal animals' eyes (especially cats - and causes the eyeshine effect).

But I'm not volunteering! Miaow!

[BAZ Senior]

That or it blurred their vision making their suitors appear more attractive to them!

The alternative is to self medicate with alcohol, and it also lasts about twenty four hours.

[Tim]

Interestingly I was talking to a seasoned astronomer who was describing the day he met a guy who does really detailed sketches of DSOs with far more detail than you would expect.

He said his pupils were much larger than normal.

It's anecdotal, but I wonder whether there is some truth behind the story?

[starstalker]

Interestingly I was talking to a seasoned astronomer who was describing the day he met a guy who does really detailed sketches of DSOs with far more detail than you would expect.

He said his pupils were much larger than normal.

It's anecdotal, but I wonder whether there is some truth behind the story?

you know theres other subsctances that are not that legal that can open your pupils and allow you to see things with a lot more "detail" lol:D

[Macavity]

There are the anecdotes about Isaac Newton experiencing significant discomfort (and Scotoma - Blind spots?) when SUDDENLY exposing a fully dilated pupil to a shaft of bright sunlight in a darkened room. But probably you won't be repeating his pioneering experiments on spectra?

[JamesC]

I'll confess I experimented with some over the counter eye drops that claimed to have some pupil dilating effects. The drops were really puny compared to what opticians have - I couldn't honestly discern much effect.

I'm less interested in pupil size these days. I think your eyes just dark adapt until sky glow is the limiting factor. Maybe if you went into space or something pupil size would count more (or if staying dark adapted is difficult because of lights).

Worth getting to know your eyes though - I recommend going somewhere really dark and covering each eye alternately and noting the difference. I am very short sighted and the edges of my cornea/lens are bad. I get little spikes coming off stars. If I look through 10x50 binoculars then the spikes are very much smaller. If I move the binoculars around I can sample different parts of my cornea. Actually if I move a finger in front of my eye to block bits of my cornea off I can see the spikes disappearing. I know the spikes from my eyes quite well and I can tell how dilated my pupils are by how big the spikes are! It's funny seeing them vary over the night as my alertness changes. Don't assume that the eye that is better at larger exit pupils is also better at smaller exit pupils, although hopefully it doesn't make any noticeable difference.

[umadog]

Interestingly I was talking to a seasoned astronomer who was describing the day he met a guy who does really detailed sketches of DSOs with far more detail than you would expect.

He said his pupils were much larger than normal.

It's anecdotal, but I wonder whether there is some truth behind the story?

Not unless he was using an eyepiece providing a sufficiently large exit pupil: http://d1w59n850sno2b.cloudfront.net/Exit-Pupil_binoculars.jpg (see the top image pair).

In most circumstances (even for DSOs) we often eyepiece exit pupils smaller than the eye's pupil diameter. I know I do plenty of DSO observing in the 5 mm to 2.5 mm exit pupil range.

[LukeSkywatcher]

I have had these drops put in twice. Man o' man do they sting. The last time i had them in, it was a bright sunny day and i had to sit in the hospital for over 2 hrs before i could venture out to get a bus. The sun was blinding.

They would be terrible to use for astronomy. Every single point of light would have lots of diffraction spikes and the glare is horrible.

[JimStan]

When I have had those drops in, everything gets halos around them. Street lights are especially noticable for that effect, and the general contrast drops dramatically, even if I wear dark sunglasses ! Not something I would recommend under any but medicinal circumstances !

Jim S.

[LukeSkywatcher]

Its probably better to use Optrex. If nothing else they leave your eyes feeling revitalised and refreshed.