# Why did I see red triangles? Visual hallucination? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [August 30, 2020, 3:31pm UTC](https://boards.straightdope.com/t/why-did-i-see-red-triangles-visual-hallucination/919374 "2020-08-30T15:31:28Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![snowthx](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/snowthx/32/10660_2.png) [@snowthx](https://boards.straightdope.com/u/snowthx)\ **Post date:** [September 11, 2022, 11:57am UTC](https://boards.straightdope.com/t/why-did-i-see-red-triangles-visual-hallucination/919374/21 "2022-09-11T11:57:50Z")
I’ve known what is being described here as [floaters and flashes.](https://www.aao.org/eye-health/diseases/what-are-floaters-flashes) ---
**Author:** ![John\_DiFool](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_difool/32/19543_2.png) [@John\_DiFool](https://boards.straightdope.com/u/John_DiFool)\ **Post date:** [September 11, 2022, 12:47pm UTC](https://boards.straightdope.com/t/why-did-i-see-red-triangles-visual-hallucination/919374/22 "2022-09-11T12:47:30Z")
Alas @Dingbang hasn’t been on in 18 months (the @ will send him a notification, if he has such enabled). ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [September 11, 2022, 3:33pm UTC](https://boards.straightdope.com/t/why-did-i-see-red-triangles-visual-hallucination/919374/23 "2022-09-11T15:33:10Z")
Probably due to the brake lights being arrays of LEDs. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [September 11, 2022, 6:43pm UTC](https://boards.straightdope.com/t/why-did-i-see-red-triangles-visual-hallucination/919374/24 "2022-09-11T18:43:37Z")
Pretty sure you are right. Circular halos around lights are common especially with aging eyes in low light circumstances. Such as from astigmatism, cataracts, or even with presbyopia. My guess is the individual red LEDs are each creating circular halos, which overlap, interacting to create illusory triangles. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [September 12, 2022, 2:18pm UTC](https://boards.straightdope.com/t/why-did-i-see-red-triangles-visual-hallucination/919374/25 "2022-09-12T14:18:49Z")
An example of how one set of shapes create the perception of other shapes that override is this one: > **[People are losing their minds over this circle-filled optical illusion](https://www.upworthy.com/amp/optical-illusion-circle-filled-2657648640)** > > The 'coffer illusion' and was created by a Stanford University psychologist. In fact neither the circles or the rectangles are really there: our brains creates them. The idea would be that the multiple diffraction halos overlap to create intersecting brighter spots that hit the retina in a pattern that the brain fills in as triangles. @ChrisJD and @Dingbang - you can test with a single bright red LED at a distance in low light and see if you get a single dim circular halo and also check out the stop lights it happens at to see if they actually are arrays of LEDs. Possibly offset rows inside the circle that is the light. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [September 12, 2022, 3:24pm UTC](https://boards.straightdope.com/t/why-did-i-see-red-triangles-visual-hallucination/919374/26 "2022-09-12T15:24:41Z")
Sorry for the multi post but look at the unilight one below and you can see how offset lines can create triangles. > **[LED Traffic Lights: lanecontrols.com (ITS)](https://lanecontrols.com/?gclid=CjwKCAjwsfuYBhAZEiwA5a6CDPFlYqKDR5vnYHbo7dgiXhVdm84BUpTKvkdreAL0JcOVUuGmjiSl_xoCwncQAvD_BwE)** > > Industrial Traffic Solutions designs and manufactures custom LED Traffic Lights and Industrial Traffic Control Systems. Call us at: (813) 920-9357. Cones, which see red, are more sensitive in low light and more concentrated in the fovea. I’ll shut up now. ---
**Author:** ![HyKris](https://avatars.discourse-cdn.com/v4/letter/h/c68b51/32.png) [@HyKris](https://boards.straightdope.com/u/HyKris)\ **Post date:** [December 19, 2022, 4:27am UTC](https://boards.straightdope.com/t/why-did-i-see-red-triangles-visual-hallucination/919374/27 "2022-12-19T04:27:21Z")
I’ve been searching all over the internet for this exact thing, and it has led me here. One day I suddenly noticed the red tail lights appeared to look like triangles, and now it feels like it regularly occurs. It is also exactly as you have described. Weird. ---
**Author:** ![Cari](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cari/32/13198_2.png) [@Cari](https://boards.straightdope.com/u/Cari)\ **Post date:** [January 20, 2023, 4:01am UTC](https://boards.straightdope.com/t/why-did-i-see-red-triangles-visual-hallucination/919374/28 "2023-01-20T04:01:19Z")
The exact same thing happened to me for the first time at night. I was coming back from the grocery store and at first, I saw a cluster of red flickering lights in a clump far ahead in the road and thought they might be some sort of emergency vehicles, but then all of the red lights on the cars formed into triangles with black centers. There was no dizziness and no other symptoms whatsoever. I’m a teetotaler. I hadn’t eaten anything strange. Nothing like this has ever happened to me before. ---
**Author:** ![Markusstill](https://avatars.discourse-cdn.com/v4/letter/m/e19adc/32.png) [@Markusstill](https://boards.straightdope.com/u/Markusstill)\ **Post date:** [March 24, 2024, 6:31am UTC](https://boards.straightdope.com/t/why-did-i-see-red-triangles-visual-hallucination/919374/29 "2024-03-24T06:31:02Z")
Hi Bingbang & Cari! Yes, tonight for the first time, all red lights (tail lights, traffic lights, and distinct red reflectors on things like mailboxes) appeared as vertical triangles. I wear 1.75 reading glasses, but I have fairly good long-distant vision. Tiny, distinct LED taillights appeared to be 4-inch-tall triangles @ 20 feet, while average-sized tail lights appeared to be 18-Inches tall @100 yards/3-feet tall @ 200 yards/4-and-1/2 feet tall @ 300 yards. The only two things different about my day leading up to this night drive was 1.) Handling a large amount of paper currency (100 dollar bills) when selling an antique vehicle, and eating at a relatively high-end Chinese food restaurant. I wondered if the currency might have come in contact with some kind of hallucinogenic drug exchange, or whether some special shellfish extracts/ingredients might have been in my Chinese food’s Shrimp in Lobster Sauce. While the observations were very distinct (‘looked like bright red caution triangles mounted on the back of cars & semi’s at first), it didn’t hurt, it didn’t impair my driving, and the only concern to me was my brain (was it a symptom of some kind of retinal/optic nerve degenerative disease symptom?). I’m just so glad that I was not the only one, thank goodness! Hey guys, let’s see if we can get to the bottom of this anomaly, okay? ---
**Author:** ![Markusstill](https://avatars.discourse-cdn.com/v4/letter/m/e19adc/32.png) [@Markusstill](https://boards.straightdope.com/u/Markusstill)\ **Post date:** [March 24, 2024, 7:04am UTC](https://boards.straightdope.com/t/why-did-i-see-red-triangles-visual-hallucination/919374/30 "2024-03-24T07:04:44Z")
By-the-way, I’ve never done drugs, and I hadn’t consumed any alcohol in the previous 22 hours. I honestly feel like something was in my dinner that might have reacted with my routine supplements, effecting my retina’s red-sending rods (or the brain’s perception of it). I’ll be scheduling an eye appointment next week, and I’m hoping that this will be a fairly routine observation with a quick fix. ---
**Author:** ![Markusstill](https://avatars.discourse-cdn.com/v4/letter/m/e19adc/32.png) [@Markusstill](https://boards.straightdope.com/u/Markusstill)\ **Post date:** [March 24, 2024, 7:20am UTC](https://boards.straightdope.com/t/why-did-i-see-red-triangles-visual-hallucination/919374/31 "2024-03-24T07:20:32Z")
One last thing: I have some left-overs from that restaurant. I’m going to eat something “normal” tomorrow evening, and try to replicate the triangles tomorrow night. Then, on the next night, I’ll consume the leftovers, and go look to see if the symptoms return. ---
**Author:** ![Free\_butterfly28](https://avatars.discourse-cdn.com/v4/letter/f/e9bcb4/32.png) [@Free\_butterfly28](https://boards.straightdope.com/u/Free_butterfly28)\ **Post date:** [August 15, 2024, 8:16am UTC](https://boards.straightdope.com/t/why-did-i-see-red-triangles-visual-hallucination/919374/32 "2024-08-15T08:16:53Z")
I need help, this is happening to my like for two weeks already I keep on looking online for answer but nothing to explain this. Only your comment describes everything happening to me with the exception that it also happens with the fellow lights. It’s driving me crazy. Every yellow or red light turn into vivid red triangles, sometimes they can look like double. Do you have any update for your case? I went to the eyes doctor he changes my glasses I was expecting for it to stop. But no it didn’t it’s still the same Ms what can I do? ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [August 15, 2024, 3:26pm UTC](https://boards.straightdope.com/t/why-did-i-see-red-triangles-visual-hallucination/919374/33 "2024-08-15T15:26:35Z")
Welcome to the board. Maybe you can help proof my hypothesis of Sept ‘22? Is it also in low light circumstances and with lights that consist of LED arrays? If looking at a _single_ LED light in low light at a distance do you perceive a halo around it? Thanks. ---
**Author:** ![Free\_butterfly28](https://avatars.discourse-cdn.com/v4/letter/f/e9bcb4/32.png) [@Free\_butterfly28](https://boards.straightdope.com/u/Free_butterfly28)\ **Post date:** [August 16, 2024, 3:19am UTC](https://boards.straightdope.com/t/why-did-i-see-red-triangles-visual-hallucination/919374/34 "2024-08-16T03:19:19Z")
Yes it only happens at night. They are brighter and stronger in low light scene, but I can still see them while driving in the city, just with a lower intensity. But it’s very weird the yellow light on the trucks. Did you went to a neurologist ? What can be wrong? Why is this happening to us? ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [August 16, 2024, 4:24am UTC](https://boards.straightdope.com/t/why-did-i-see-red-triangles-visual-hallucination/919374/35 "2024-08-16T04:24:52Z")
I have not experienced this specific visual illusion myself. I just am understanding why it occurs. See post 23 and following. There is nothing wrong. Diffraction halos (a perceived ring of light around the light) occur from LEDs in most of all in low light situations, especially in those who are far sighted (which occurs normally with aging, called presbyopia, literally “old age vision”), astigmatism, or cataracts. Multiples of these circles overlapping from LEDs in arrays induce a visual illusion, creating illusory triangles. There are two main groups of receptors in the human retina: rods that only distinguish black and white and are less sensitive in low light, and cones, which are more sensitive in lower light and which distinguish colors. The most numerous cones, the L cones, have peak sensitivity in the red to yellow range. These are the receptors responding to these diffraction halos and whose signals are processed to create the illusion. I hope that makes sense. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [August 16, 2024, 2:05pm UTC](https://boards.straightdope.com/t/why-did-i-see-red-triangles-visual-hallucination/919374/36 "2024-08-16T14:05:45Z")
I don’t think this is the same thing as the OP, etc., but it’s still a weird coincidence. Last night as we were driving home the setting sun was behind me and I kept briefly seeing two thin horizontal red lines flash across the speedometer cover. I was driving so investigating it while moving was out of the question. I was going to check it out at the next red light but I got green all the way along that stretch and it didn’t recur the rest of the way. I kept thinking, “Great, I read a thread about this stuff and _now_ I’m seeing things.” ---
**Author:** ![curious\_one](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/curious_one/32/18917_2.png) [@curious\_one](https://boards.straightdope.com/u/curious_one)\ **Post date:** [April 3, 2025, 3:42am UTC](https://boards.straightdope.com/t/why-did-i-see-red-triangles-visual-hallucination/919374/37 "2025-04-03T03:42:49Z")
I have been seeing these triangles that show up on red tail lights for a while. Its always at night, and at a certain distance–perhaps 50 yards or so. I have watched them go from triangles with the dark center, back to all the variations of tail light shapes, and back again to triangles as the traffic moves farther away. I am farsighted, and have aging eyes needing 2.0 reading glasses. I assumed something was changing in my eyes, so I did a search to discover any other people having this experience. The explanations of LED lights intrigues me. But in my case it has nothing to do with any drugs or alcohol, migraine headaches, seizures of any kind, dirty windshield, nor is this a “halo”. It is a distinct triangle, very defined red lines around a dark black center. But what if it is something in the LED light interacting with my older eyes. And I wonder if the variety of people who don’t experience this strange phenomenon, might be younger, or have healthier eyes. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [April 3, 2025, 7:22pm UTC](https://boards.straightdope.com/t/why-did-i-see-red-triangles-visual-hallucination/919374/38 "2025-04-03T19:22:58Z")
Welcome. You are another data point supporting my hypothesis: an association with presbyopia and/or cataracts. Again the proposed mechanism goes that a single LED point causes a diffraction halo and the overlapping halos in an array through visual system processing (on off cells etc) creates illusory triangles. At that point no halo is perceived, triangles are. ---
**Author:** ![Dingbang1](https://avatars.discourse-cdn.com/v4/letter/d/9fc29f/32.png) [@Dingbang1](https://boards.straightdope.com/u/Dingbang1)\ **Post date:** [April 3, 2025, 7:34pm UTC](https://boards.straightdope.com/t/why-did-i-see-red-triangles-visual-hallucination/919374/39 "2025-04-03T19:34:53Z")
Hello everyone, checking in five years later. I still see the red triangles and have just accepted it. Thanks for everyone sharing their own experiences and for the possible explanations. For the record, I haven’t had any other health issues or troubling symptoms, I haven’t had hibiscus since that incident, and I don’t notice any correlation with other possible causes. DSeid’s explanation seems the most on point, if I’m understanding correctly that it can produce my very well delineated triangles with three clearly visible sides. Thanks. ---
**Author:** ![Kent\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kent_clark/32/105_2.png) [@Kent\_Clark](https://boards.straightdope.com/u/Kent_Clark)\ **Post date:** [April 3, 2025, 9:08pm UTC](https://boards.straightdope.com/t/why-did-i-see-red-triangles-visual-hallucination/919374/40 "2025-04-03T21:08:02Z")
> [@Dingbang1](#): > > I still see the red triangles and have just accepted it. Have you had your eyes checked for cataracts? That’s a call for an opthamologist to make, not just your optometrist. For me, it was getting a new pair of glasses, then realizing I saw two distinct bright circles when I looked at traffic lights. I went back to my trusted optometrist, she did a couple of quick tests and told me to see a full-fledged opthamologist. [Previous page](https://boards.straightdope.com/t/why-did-i-see-red-triangles-visual-hallucination/919374.md?page=1) [Next page](https://boards.straightdope.com/t/why-did-i-see-red-triangles-visual-hallucination/919374.md?page=3)