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Comment by sqlftw | Hacker News Reader

Many years ago I tried LSD, and for whatever reason, I never seemed to experience visual hallucinations. However, in recent years, cars have started having LED tail lights, which really bother my eyes. Several times I have asked my friends, "Aren't those terrible!?" to which they might reply, "They are pretty bright." Bright! They aren't just too bright, they are intensely STROBING! Can normal people not see that? Is this the flashback I was promised?

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Low frequancy PWM is annoying, it's not just you:

http://www.candlepowerforums.com/vb/showthread.php?104151-Ir...

Interesting video of the effect: https://www.youtube.com/watch?v=_XpGUYbehSk

EDIT: Well, I thought it was interesting anyway... my ability to perceive flicker deteriorated markedly after the age of 30 but this way I can at least see how the camera sees it! (I will be keeping an eye out for this phenomenon now but I doubt I could spot it any more unless right out of the corner of my eye.)

Yeah, I really think the NHTSA should mandate a much higher minimum frequency.

They should limit the brightness as well, pulling up behind one at a stop light at night is blinding.

I hate to continue your tangent but I do feel something that is relevant to the OP article are new vehicles that have blinking break lights.

Most people don't notice these new break lights (I think its on Chevy cars) but when the driver breaks there is a very fast and subtle blinking of the red tail lights (opposed to just the red tail lights being on for older cars).

I only noticed this blinking while under... but now I see it often but my wife does not. ie its similar to the pong bar "C" letter in the article.

"Brake" lights, not "break" lights.

Yes... that was dumb (and even twice!)... I know how to spell brake.. I'm not sure what happened :)

A kid I went to school with would be driven mad by fluorescent lights flickering, even if no one else could see it.

I have no reason to think he had been taking hallucinogenics as a preteen.

I get visual migraines and your comment reminds me of the experience. Perception of light is often out of the norm for me. Sometimes I will see lights that aren't there. Sometimes I will have certain visual triggers for these effects.

There is some evidence that psilocybin in low doses (much lower than "effective for recreation") can ameliorate or even cure migraines. I mention this as I have a member of my family that suffers from terrible periodic migraines and I myself experience migraines at least once a year.

Many current migraine treatments (such as triptans and ergotamine) are serotonin agonists designed to induce vasoconstriction. The "classic psychedelics" are also serotonin agonists.

Migraine treatments target different subparts of the serotonin system than psychedelics do (migraine: primarily 5HT1B/5HT1D vs psychedelics: 5HT2A). However, from what I see, a lot of the classic "popular psychedelics" don't tend to be very selective, and act on a lot of the serotonin system as well as other systems such as glutamate (5HT2A agonism by itself is not necessarily psychedelic).

Consequently, LSD for instance seems to have quite an affinity for 5HT1B (with a touch of 5HT1D), and psilocin for 5HT1D (and a touch of 5HT1B). So reports of LSD and psilocin being effective against migraines aren't surprising.

LEDs use pulse width modulation to dim, so if it's a subpar circuit with relatively large width duty cycle, that might be what you're picking up. Might want to check out persistence of vision displays. They rely on tricking your brain in similar ways.

Do florescent lights bother you too at all?

Also from what I've heard sometimes people will only see visuals after a second time taking LSD or by taking a more substantial sized dose.

I've got some screwy eyes (astigmatism, nystagmus, myopia) and have definitely noticed that sometime over the last few years the lighting situation has gotten more annoying. Some things I've noticed are particularly annoying:

The screens of cellphones and certain OLED displays having visible screen refresh rates, especially if my eyes are panning across them from a distance.

Shitty LED display lighting with a visible flicker. It's especially bad on a place nearby that has window frames outlined in what are effectively Christmas lights--almost enough to give me a headache just looking at them.

Certain LEDs and phone backlights tend to leave trails in the dark (once my eyes are accustomed to it). This is probably normal, but is a little disconcerting.

Projected images can have minor chomratic aberration, which can be distracting during a presentation. If I twitch my eyes purposefully back and forth, it gets worse.

I love graphics, but that shit is annoying IRL.

I see the strobing of LEDs if the lights are moving across my field of vision. I find it a pretty distracting as well.

This is because, as the source of light is moving across your field of vision, it is exciting different areas of your retina. With a stationary light source, persistence of vision (POV) would make the light source appear continuous, uninterrupted, because the rods/cones do not have time to clear the signal. You can perceive the LED being switched on and off as POV does not come into play.

This must be what I experienced this weekend. I was trying to take a picture of some LED light fixtures and they were doing a number on my camera's sensors. Black bands that at certain angles would move across the screen even though the camera and the lights were stationary.

I don't think it has anything to do with LSD. I've never tried LSD, but I also see moving LEDs (especially white ones) strobing that happens very fast and it's more like they are vibrating. It's hard to explain this feeling, but it's very distinct and distracting.

I have had rainbow halos around street and car headlights since my early twenties. I first noticed it whilst tripping and have yet to determine whether the cause is physical or mental. Looks pretty though.

You noticed a change in your vision and you didn't go get it checked?

I've had that for as long as I can remember, I'm pretty sure its a light reflection/refraction kinda thing.

A lot of that stuff is always there - just think of the hundreds of optical illusions that can be constructed! - but until it's connected with an emotional experience during a trip, the brain doesn't single it out.

The effect that jumped out at me was focusing at a spot on the floor while standing up and turning. It creates the momentary impression of a spiral pattern in my perception. Especially with a dot-like pattern on the floor :)

Also, if you like rainbow halos, you might also like Shock Diamonds: https://www.google.com/search?q=shock+diamonds&source=lnms&t...

I've had something similar since at least my teens. At night if I look closely at streetlights, I see what looks to me like a magnetic field around streetlights. I don't think that's what I'm actually seeing, but that's what it looks like.

You should have your eyes checked. Halos around bright light sources may be caused by cataracts.

Cataracts generally affect the elderly, but young people may also have it due to genetic factors or medication (such as corticosteroids).

As mentioned in another message, you may have astigmatism. I get triangular spikes off of relatively point-sources at a consistent angle of about 10 degrees clockwise from vertical from my astigmatism. Your angle will vary, of course.

This could be HPPD[1] or related. There seems to be uncertainty as to if hallucinogens cause some of these effects directly, or if they simply help train the mind to notice what was already there. For instance, is visual snow there already, and hallucinogens simply make one more aware of it and capable of focusing on it (similar to how tinnitus is worse if one focuses on it)?

https://en.wikipedia.org/wiki/Hallucinogen_persisting_percep...

This can also be caused by (minor) eye issues. I had that effect for a while after PRK surgery.

Many people find this condition extremely debilitating:

http://hppdonline.com

There is a lot of pain, anguish and regret expressed on the forums by people suffering with this condition.

You may have astigmatism or some other more "mundane" issue there. I see them partially too, but it's astigmatism, because when I put on my glasses they go away. Some do it more than others, but that may be related to the spectrum of the light, which varies quite substantially.

(On that note, here's an old HN post I recall about how to cheaply and easily see light spectrums: https://news.ycombinator.com/item?id=971413 Of course you can't do that with car lights very easily, but you can still check incandescent vs. florescent vs. LED, etc. fairly easily, and perhaps learn to correlate which is which when you see the "rainbows".)

Thanks for the link.

I thought it could be something to do with my eyes but never thought it could be corrected. Looks like I'm due an eye check! Last time was when I was 6 I think..

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