Is there a poison that could kill someone with a small dose to the eye?

I am new here so I hope this is the right place to ask this! I'm not a writer by any means, but I am trying to write a little murder mystery for a group of my friends.

The idea is that the victim will be killed by some kind of poison that was on the tip of a needle attached the their reading glasses. The needle will prick them in the eye when they put the glasses on. They will obviously be aware that they've been pricked in the eye, so it needs to be a fairly fast acting poison that kills them before they realize whats happened. The poison also would ideally not show up in an autopsy.

I know it's a bit far fetched that they wouldn't see the needle on their glasses, but I'm leaning on the fact that they are extremely nearsighted and the needle is very small. Being that it's just a little game for my friends, I'm okay with a bit of a stretch.

Is there any chance that there is a poison that would kill in this way? I've done some google searching but haven't been able to find much.

• Why the eye? It can be more dramatic, but the needle will stick out a lot. If you put a tiny, tiny needle on one of the hooks for the ears, it won't stick out as much ánd can be hidden by both the ear and the hairline. In the eye it could be more visible, as it is the of the things people look at. – Trioxidane Sep 23 '20 at 6:25
• Easier to put a small needle on the frame of the glasses to puncture the skin. That requires only the tiniest of needles, whereas the eye would require a large one. Trying to puncture the eye is just way over-complicated and even using the eye-glasses is pointless. Ask V. Putin.. – StephenG Sep 23 '20 at 10:31
• As a matter of ethics I would discourage publicizing information about poisons that do not show up in autopsy (or are very unlikely to be detected). – StephenG Sep 23 '20 at 10:33
• If you can get close enough reliably to the victim for long enough unobserved to glue a needle to their eyeglasses (or exchange their eyeglasses), then you can commit the murder many easy and less-convoluted ways. Remember to change the prominent clock on the mantelpiece so all the witnesses give the police the wrong time, thereby establishing your perfect alibi. – user535733 Sep 23 '20 at 15:10
• Until I read the "not showing up in autopsy" requirement, I was gonna suggest chlorine trifluoride. A little bit of that will kill you quite dead. – Cadence Sep 24 '20 at 18:51

Botox

The estimated human lethal dose of type A toxin is 1.3–2.1 ng/kg intravenously or intramuscularly, 10–13 ng/kg when inhaled, or 1000 ng/kg when taken by mouth.

No-ones calculated $$LD_{50}$$ for botox via eye, but I bet it'd be small enough. I don't think it needs to actually pierce the eye - mixed with a drop of lubricating eye drops it could form a deadly tear drop, which gets absorbed through the tear duct.

I don't know if it'll be detected in an autopsy, but it is injected for plastic surgery so there's a potential for plausible deniability.

• Botox is derived from the bacterium Clostridium botulinum which is a strain of bacteria often associated with food poisoning from improperly packaged can foods. So, even if the person is not using it cosmetically, plausible deniability is not a problem – Nosajimiki Sep 24 '20 at 18:57

Various nerve agents. 10 mg of VX on the skin are lethal. It takes only slightly more Sarin. The problem, of couse, is that you cannot simply buy them in the next drug store. And it is difficult to handle, but compare the death of Kim Jong-nam.

Easy, Actually.

And relatively inexpensive to source as well. Any of the several organophosphates used as pesticides in ag applications could be used. VX and sarin are in the organophosphate category; they're much harder to source though, as they're protected class chemical weapons. Organophosphates don't require injection, are hard to identify before causing irreversible damage, and mixed with a fast acting sedative, such as that used in a medical or veterinary practice, would ensure that the victim doesn't have the time to call for help before ingesting a fatal dose.

Gruesome, but agricultural chemicals are some of the deadliest still available today. On a side note, agent orange is still used as a cleaning substance on dairy farms...