A question about doubled depth perception or wonky binocular vision
June 27, 2020 3:49 PM   Subscribe

I experienced a brief moment of depth-perception weirdness today, and I'm interested in finding a clear explanation.

Earlier today, I trimmed my hair, then showered off any stray bits over the bath. I stood up and opened my eyes, and saw two versions of the bathroom wall about two feet in front of me, one a few inches closer than the other. This immediately struck me as quite trippy, like looking at an old 'magic eye' poster. After a couple of seconds of looking at these two overlaid views, I lifted my right hand up to touch the version of the wall nearest me. My hand went through that wall, and carried on for a couple of inches until it met the rear (real) wall. I blinked a couple of times, and everything was back to normal.

To be clear, I'm not at all concerned that this was anything other than a one-off biomechancal glitch of some kind. My eyes feel fine and normal. I'm just interested in the how and why of what I experienced.

Both versions of the wall were in focus, so I'm guessing that my binocular vision must have gone screwy somewhere. But how, and what was going on with my eyes and brain?
posted by pipeski to Science & Nature (14 answers total)
Standing up quickly has sometimes caused me to feel a little lightheaded and also temporarily reduce vision (sometimes blacking out one eye entirely). This is more likely to happen when my iron levels are low and I'm mildly anemic. Lack of blood to the brain does funny things. I don't recall having this kind of double vision happening but I wonder if it's the same kind of thing - a temporary reduction of blood flow to the brain or eyes causing strange things to happen.
posted by acidnova at 4:05 PM on June 27, 2020 [1 favorite]

Response by poster: I've experienced a similar thing to that, including that feeling of darkening vision, and it wasn't like that in any way. Misbehaving eyes apart, I felt perfectly fine.
posted by pipeski at 4:11 PM on June 27, 2020

Best answer: One of my eyes has got a wee bit lazy in middle age, and occasionally when I'm tired or I've had too much coffee I get something like what you've described. Everything snaps back to normal quickly once the wandering eye lines back up with the other but yeah it's quite an odd feeling while it lasts.
posted by Mary Ellen Carter at 4:28 PM on June 27, 2020 [3 favorites]

Yep, I discovered this as a child while looking at repeating tiles. You can cross your eyes slightly and fake out your depth perception. Can be a bit trippy at first.
posted by sjswitzer at 4:36 PM on June 27, 2020 [7 favorites]

Best answer: I was wondering if your hair trimming had you intently, but unknowingly, crossing or otherwise straining your eyes for awhile, because "When the eyes are misaligned, the brain receives two different images." (Strabismus (Crossed Eyes), American Optometric Association).
posted by katra at 4:53 PM on June 27, 2020 [1 favorite]

Were you kneeling over the edge with your head down (like I would do buzzing my head with trimmers) and then showered off your head before standing up? If so, that's probably blood pressure combined holding your breath (to avoid drowning), having your body slow down a bit and then standing up and having all of the blood pooled in your head make a quick retreat to the rest of your body. For a moment your eyes had different focus and hadn't aligned and things looked weird.

Trippy is right, that slightly off same-focus and not quite aligned is the basis of trippy LSD effects of breathing walls and seeing faces in the carpet or looking at a stucco ceiling and seeing it shift and merge and turn into layers of dark and light like lace and move around. Because your eyes are twitching a bit and aren't in close sync so you start perceiving depth where there isn't really any. Yeah, sorta like magic-eye pictures. You can sorta do this while not tripping if you really try, tripping you can't really control it.

I vote momentary loss of oxygen levels and blood pressure.
posted by zengargoyle at 4:56 PM on June 27, 2020

if like me, you try and trim your neckline looking in a vanity mirror trying to see another mirror you are hand holding to see your neck while juggling a trimmer, that already gets tough on the eyes for depth perception and mine take a while to focus properly after. Combined with bending over for an extended period, vision things could go wrong easily. (my barber is worth his inexpensive fee just for my neckline, the rest i can buzz fairly easily with practice, first time had random hair tails in the back).

If it happens frequently, or in other conditions, obviously see a doctor.
posted by TheAdamist at 5:46 PM on June 27, 2020 [1 favorite]

Best answer: Purely anecdotally, I am able to do this with my vision at will and have been able to do so all my life. I think of it as 'unhooking' my eyes from each other. For me it feels restful, as though my eyes have to work slightly harder stay in true focus. As a data point, I'm extremely short-sighted - so bad that some brands of contact lenses don't even offer correction at the level that I need. There's never been a problem with returning to normal vision from my 'doubled' state.

I'm actually surprised and interested by this thread as I have always believed that everyone experienced this.
posted by DSime at 6:26 PM on June 27, 2020 [3 favorites]

sjswitzer is almost certainly right.

If you have a repetitive tile pattern, your eyes can have the same image when one of them is actually shifted one unit to the left or right. Your eyes were actually converged in front of the wall when you thought they were converged right at the wall. If we knew exactly how far you were from the wall and where the false wall seemed to be, we could probably guess how big the tiles are because both walls being in focus means the real wall must have been just far enough behind the illusion for the perceived patterns to coincide again.
posted by jamjam at 6:35 PM on June 27, 2020 [3 favorites]

Your mention of "like magic eye" is pretty much dead-on.
A place I used to work had this horrendous wallpaper in the restrooms - gold tracing on maroon. The pattern repeated about every 2.5 inches. Whenever I used the urinal, I'd get my eyes to do the same thing - cross them just enough to get them focused on a different repetition. Kinda trippy.
posted by notsnot at 6:55 PM on June 27, 2020 [2 favorites]

This is a Magic Eye poster thing. Happens with any repeating pattern. All the rage in the 90's.
posted by sanka at 8:39 PM on June 27, 2020 [1 favorite]

More anecdata, I am also extremely near sighted, and can also do this at will on repeating patterns. It would happen a lot to me once my glasses prescription start to get bad - especially with chain link fences. I always just thought that because I couldn't see small details, it was easier for my eyes to think that one link and another link were identical, and they would independently focus on 2 different points. My ceiling in my bedroom is ridged, and it happens there, too, with the shadow stripes.
posted by FirstMateKate at 8:13 AM on June 28, 2020 [1 favorite]

Best answer: Yes, also nearsighted with an astigmatism and an eye that gets lazy when I get tired and this often happens to me accidentally. Ironically, I wasn't able to do magic eyes until I found ones with dots like this. Once I realized that you were supposed to let your eyes cross into double vision I could do it very easily.
posted by PhoBWanKenobi at 10:28 AM on June 28, 2020 [2 favorites]

Response by poster: Thanks all. I've marked as best the answers that are closest to the way I experienced the phenomenon, which in no way indicates that the other answers wouldn't be helpful in a similar case. I don't think this was the 'magic eye' effect as such, as it didn't seem to be based on repetition - the two images were clear and distinct, whereas my experience with the 'magic eye' effect is that it requires you to overlay two copies of the same pattern.

On reflection, I think what happened is that my right eye turned to the left slightly. That eye did 'feel' like the one causing the double vision. I think that, although both eyes were correctly focused, they must have been giving different 'angle' signals to my brain, leading to different depth values. .

I'm surprised that I haven't experienced this before. I'm nearsighted, have astigmatism, and also an inherited tendency for one or other of my eyes to wander off course when I'm especially tired. First time I've seen this effect though.
posted by pipeski at 4:36 AM on June 29, 2020

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