The question came up at home because we had a clear 1/4 moon on the sky. I was looking at it with both eyes open but i’d see it overlapping, I thought it was similar to when you put a finger in front of your eyes and they both look at it from a different angle resulting in a double image.
But upon closing one eye i could still see it double
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Do you wear eyeglasses, or were you looking through any lens or window? (Just ruling out some basics. )
Impossible unless you wear glasses or were looking through a lense or a pane of glass like a window to see the moon.
Possibly it was just blurry due to lack of focus and you thought you saw two.
Can happen if you have tears on your eye, or you have astigmatism, or you are squinting which puts pressure on your cornea which produces an effect similar to astigmatism
You might have a dominant eye. I have a high degree of astigmatism on my left eye and my brain usually defers my field of vision to the right eye. As a kid i needed to wear an eye-patch and do exercises so my brain wouldn’t totally shut it off.
When there are strong discrepancies between the image processing between the pair, the brain will split the vision.
People with perfect vision see like a widescreen tv. The brain “ignores” the bridge of the nose and forms an entire image comprised of both left and right signals.
Are you able to see 3d movies, books?
I’ve had this happen with dry eyes (seeing double with one eye shut)- my eye doc said that was normal and that dry eyes can do a lot of funky things to your vision. But also, I’m sure a doctor could identify what’s causing it for you if you’re concerned about it
Tension in your eye muscle<->neck muscle<->sternocleidomastoid muscle complex that causes fatigue to your non-major eye to focus. Can be caused by a forward head posture from too much sitting and staring on a computer screen or a mobile phone.
It’s called mono ocular diplopia- most commonly caused by your lens of eye being out of focus. There are more than a dozen reasons on why that happens!
In addition to the other answers – there are some conditions that can cause double vision even with only one eye open. Diabetes is the most common one – it happens because of damage to either the nerves (resulting in a faulty signal going to the brain) or blood vessels (resulting in a distorted lens) in the eyes. Happens most often with bright objects.
If it was an isolated thing, then it’s probably a result of artifacts only present at that time – something like water or dust in your eye. But if you notice that you see double with a lot of different objects, it might be worth going to see your doctor and getting tested for diabetes.