It's funny - "double vision" can mean a few different things (to me, at least):
In one case, it's looking at something and seeing a second image of it slightly below (or below and to the side). You can see it when looking at a traffic signal - you can see the light that's on, with one below it. This can happen to people developing cataracts -- the lens, getting cloudy, carries a phantom image of the bright things, while the actual image gets through the cataract.
It's also supposed to happen if you take too much lanoxin/digoxin. There may be other medications that have this side effect. This type of 'double vision' may be unrelated to OHS.
The other kind happens when you actually see what your eyes see - as separate images. Your brain doesn't fuse the input from your eyes into a single image. This is probably the more troubling of the two - and it may prompt you to close one eye or the other to avoid confusing your brain, and making it possible to navigate. You might wait until your brain can handle the two images - either turning one off, or fusing them into a 3-d image.
I don't know if this is OHS related.
Since I stopped taking Lanoxin, and had my cataract surgeries, I, personally, rarely if ever experience the first type.
I DO, sometimes, get the second - but usually only for a few minutes, until my brain does something about it or I refuse to acknowledge it.
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BTW - to nobody in particular - the word is 'lightning', NOT 'lightening.' 'Lightening' is something some people may do to their hair if it comes out too dark, or turning an extra light on in a room that is too dark (or something). It's the opposite of darkening.
I prefer not to get hate mail about pointing this out - it's a common error.