Misaligned (double) vision visually explained

In this topic I’m providing you with a very crude, grossly oversimplified, but hopefully insightful visual explanation of how and why double/misaligned vision occurs. Keep in mind that in reality this all happens three dimensional and that this is nothing more than a schematic representation.

Motivated by @itamar’s recent question and inspired by @LegendG22’s nice myopic schematic.

First you see the emmetropic eye nicely bundling the rays of light bouncing of an object (A sign with “respect the beard!” in this case) being refracted properly into focus on the retina of the eye. As you can see, it’s all combined nicely into a single focal point on the retina and the visual cortex gets nothing but a clear image presented enabling you to see the text in complete clarity.

Next we see the myopic eye. What’s evident is that this refracted bundle of light starts to diverge again before hitting the retina. This means that the rays of light end up being spread out across the retina. By not having the object one’s looking at combined into a nice single point the rays of light get dispersed creating multiple images relayed by the retina and it’s peripheral area. Some of the light will still combine nicely in some places on the periphery creating those multiple images that you can see if you’re familiar with double/misaligned vision. This is depicted with number 2.

Some variations on this phenomena are shown with the following numbers:

  1. Very close to completely aligned vision, only a small portion of the light is out of place creating is small haze surrounding the text/object one’s looking at.

  2. The most common version of double/misaligned vision.

  3. A more potent and aggressive version of misaligned vision. The light is much more dispersed making it much tougher for the eyes and visual cortex to align this properly. This usually occurs when someone is under-corrected by too much or there isn’t enough good lighting available. Having ciliary muscle spasm can also be the cause of this happening to a greater extend.

  4. In this case there is enough light that intersects properly and comes into focus on the retina, however there are many rays of light still getting severely spread out causing a big haze surrounding what someone is looking at. Many times this is a sign that improvement is happening after reducing ones normalized correction and that our eyes and visual cortex start adjusting to bring that bundle of light into a properly focused bundle.

  5. This is pretty much how and why blur happens. That bundle of light is dispersed by so much that there’s hardly any light combining properly onto the retina or it’s periphery. There is only blur to be registered by our visual cortex and no workable image can emerge from this data.

Keep in mind that all the varieties shown in this explanation and the manner in which any of them can occur greatly depend on three main things (amongst others of course):

  • How much the distance the actual distance is between that focal point and the retina
  • The ability of the ciliary muscle to relax properly to get that focal point in the right spot
  • The way ones peripheral vision is utilized. An important part of Endmyopia is getting that peripheral vision working properly again. The more “developed” it is, the more it’s able to make out what gets projected onto it’s surface.

Thanks to Jake (of course) for checking this!

If you want to work on improving your misaligned vision, we have a nice guide for you right here: Resolving Double/misaligned vision.

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Gteat post @Laurens thank you :blush:

I have many questions that come up after reading this.
Just out of curiosity, maybe someone can add more info.

  1. what do you think affects the position of the misaligned images? In 2 it looks like they are all on the same linear plane, and on 3 they are all over the place.
  2. could the source of the double images be tiny deviations in the cornea from a perfect sphere/oval?
  3. why does the image get clearer when you stretch your eyes with your fingers? (At least for me)
  4. i did not see any word about astigmatism, do you think there is a relationship between astigmatism and double vision? Or are they mutually exclusive phenomena?
  5. is double vision and diplopia the same thing?
    https://en.m.wikipedia.org/wiki/Diplopia

I don’t expect answers, just throwing it in here…

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This helps clarify things, thanks! At least I know some of what I thought was blur is actually double vision.

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They’re 2 different phenomena. But not exclusive, you can have astigmatism as well as double vision, you can have both.
This post is only on double vision, :wink:

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That’s exactly what I didn’t want to hear. Extensive explanation by me there, just raising more questions…:wink:

In 3 the bundle of light is diverted much more so yeah, it ends up all over the map. If your peripheral vision is good you might get this, otherwise it’s just blur galore. In 2 they are much closer together and their exact position can fluctuate, remember that it’s a static representation, in real life it can move.

Could be, but if you can get clarity (with or without correction) in close-up or something distant it’s not very likely. If it’s something in the cornea it would be there always, unrelated to distance or refractive correction.

I could be that you’re shortening your eyeball manually by doing that. Wouldn’t be surprised if that’s the case for you.

Technically yes, but really it isn’t. This diplopia you are mentioning is caused by something in the body that’s going on, some disease, the muscles not working properly, over-consumption of alcohol amongst others. The double vision we are talking about is nothing more than a phenomena occurring with the myopic eye as is explained above. It’s just something refractive that needs solving and it’s just part of the process. You may see double similar to diplopia, but if you increase your correction or look at something a little closer it clears up. With diplopia it doesn’t, it’s from something else and changing what someone is looking at or the corrective lenses being utilized doesn’t solve it. Hench the difference.

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I still think what’s happening is this:

  1. You have refractive errors looking at the distance, especially myopia and astigmatism.

  2. So a blurred image lands on the retina, directionally blurred if there’s astigmatism.

  3. The visual cortex tries to fix the image. So it uses sharpening/deconvolution and pattern detection. Finding fragments of the letters, it’s able to “display” these, but it fails to determine that it’s dealing with just one letter. So you get multiple pieces that kinda resemble what it’s supposed to look like.

Peripheral vision can’t be involved here, since even a blurred letter with double vision and whatnot is still in a very small region of your field of view. Sensor cells further away are not relevant for an error like this, because all relevant input is constrained to a small region.

Using this explanation, we can also try to answer some of itamar’s questions:

If you are dealing with myopic defocus and have astigmatism, the most myopic meridian (direction of viewing in the eye) would be the direction in which double vision is most likely to occur.

Yes, unless you are dominated by spherical blur and have fragments going all over the place.

So, aspherical errors are a sufficient but not necessary condition. You just need any kind of blur that the visual cortex struggles to clean up, leading to double vision as an image processing artifact.

Of course, this won’t work if the image is too blurry. It happens most prominently when something is clear enough to work with, but not clear enough to see perfectly. This also explains why many people progress blur -> double vision -> clarity.

I’m not letting up on this theory because my eyes both have a small amount of different astigmatism, and the double vision behaves just like you’d expect from this theory. The chaotic “kaleidoscope” view is more prominent on the more myopic eye, while the directed duplication is most prominent exactly on the most myopic meridian of the more astigmatic eye. Each type of double vision disappears exactly when the corresponding refractive error is corrected.

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So this means that working on peripheral vision can solve double vision faster?

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It’s great that your more technical view on this matter is in this thread now as well. Thanks for adding it. These explanations don’t have to be mutually exclusive, they may both end up being true in some sense. Anyway, I like your addition to this post, it makes it all the more complete!

Just so we’re clear, I think your explanation makes a lot of sense. It’s just much harder to put into such a schematic :smiley:

If you want the source vector graphics file send me a PM, you can alter it to your liking.

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Thanks Laurens! Not right now, but maybe some time I can find or create some deconvolution artifacts, to show just how much they can look like double vision.

Yes, but not for the reason you think. :stuck_out_tongue: Myopia improvement is stimulated in peripheral vision, so if you work on that and the eyes shorten, the blur disappears, and then the visual system doesn’t need to sharpen so aggressively, removing the artifacts. :wink:

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@Varakari thanks for the explanation :wink:

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I thought that double vision is a brain thing, where it’s catching up in terms of processing the eye’s biological improvements. At least that’s what I thought I read on EndMyopia? So depicting double vision in terms of an optics diagram is kind of confusing to me. Most myopic eyeballs don’t see double vision, so I don’t understand how showing a diagram of a myopic eye is explaining double vision.

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You’ve read it correctly on it being a brain thing. But that’s not the whole story. It’s depicting those rays of light that are being bundled into focus breaking apart again. This doesn’t result in direct blur. Your eye can still make out what it is. Whether it’s the periphery or the visual cortex decoding it doesn’t really matter. Think of 100 balls in a straight line behind each other, if you move sideways you start seeing that it’s not just one. A similar thing happens with these light rays, it’s like a thread that’s being unraveled. Our eyes are way more complex than camera lenses in that sense, it’s not just clarity or blur. There is something in between and this just tries to explain how and why this could be happening.

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I’ve found that using a small point bright LED in a completely dark room (for example, the red power light on the corner of a TV at night) can really help visualize the various points of distortion in your diagram by varying the distance. Recently, I’ve been seeing circular radiating points—perhaps about eight nearly equidistant from the center when I’m past my edge of focus which is like your diagram’s scenarios 2 and 3 (with some other minor distortions and blur, but the points are very distinct and countable). The points get father apart with greater distance, but I can resolve them and count them even at a pretty meaningful distance. I try to “play” active focus with the dots to get them to resolve, but when they are far apart (because I’m far away), it’s impossible for me.

I suspect that this strategy can help visualize the distortions of myopia and astigmatism (I have weak to none) without any special equipment.

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I also discovered this. The tiny tv standby LED light looks like an oval of blur (which corresponds to my astigmatism power and axis) i even think i actually see patterns of my retina which is cool :yum:

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From my experience diplopia was not perceived as double vision but a distorted smooth image where I saw one leg as longer than the other when it wasn’t. It also showed up as flawed spatial perception and longer reaction time. Myopia by itself otoh doesn’t seem to have an effect on things that depend on visual processing like reading writing walking spinning in a circle etc.

And myopic dv looks like double images. Diplopia went unnoticed and disguised as ADD

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@Varakari @Laurens @Iona26 I fully agree with Varakari’s clearly-explained theory (posts #6 & #9) about the particular type of double vision described by the OP Laurens: it is an image-processing artifact due to astigmatism.

I.e., I don’t think that it results from multiple optical images in each eye, as suggested by Laurens and Iona26 in the thread A few thoughts about astigmatism from the point of view of a medical student .

Also, I’d like to nitpick on Laurens’ claim “You may see double similar to diplopia, but if you increase your correction or look at something a little closer it clears up. With diplopia it doesn’t, it’s from something else and changing what someone is looking at or the corrective lenses being utilized doesn’t solve it.” by offering 2 counterexamples:

  1. Diplopia (double vision) due to 6th nerve palsy worsens with distance, so this type of diplopia does actually clear up at close range.
  2. Concomitant diplopia can actually be corrected with lenses (with additional prism).

You aren’t nitpicking, this post and thread simply isn’t about diplopia, it’s about the double vision that occurs in reversing myopia.

So I’m not claiming anything in that regard. Like you aptly explained, diplopia is caused by something else and the way to treat it is logically different.

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@Laurens hi Laurens. Yes this thread isn’t about diplopia per se, that’s why addressing the non-astigmatism-related diplopia statement was just me being nitpicky hehe