Why is it that when a nearsighted blurry vision becomes clear when looking through a very small hole cutout?

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Why is it that when a nearsighted blurry vision becomes clear when looking through a very small hole cutout?

In: Biology

9 Answers

Anonymous 0 Comments

The problem is that the light is spread out too much rather then being properly focused. Corrective lenses fix this by focusing the light onto a smaller area. A pinhole effectively accomplishes the same, albeit at the obvious cost of field of view.

Anonymous 0 Comments

If you imagine a piece of paper pointed at an outside scene, with nothing else in front of it. The paper will just be lit white, because it’s getting light from all over the scene in front of it.

The reason a hole does what it does is because it restricts the possible directions a particular point on the paper can be getting light from.

Now imagine the paper is stuck in the back of a box, that’s entirely enclosed except for a little hole in the front wall of the box. What I’m describing is pretty much a pinhole camera.

If you imagine the top left corner of the piece of paper. You imagine you’re looking from the point of view of that top corner of paper. You can see nothing, except what’s coming through that pinhole. But because it’s such a small hole, all you can see is what’s directly through the hole in the direction you’re looking, and that’s all. You can’t see what’s directly ahead of the box from there, all you can see is what’s directly in a line from that top corner of the paper, through the hole to outside.

If you imagine that’s the case for *any* point on the paper. If you’re in the middle of the piece of paper, you can see through the hole to whatever’s directly ahead of the hole outside. If you’re at the bottom right point on the paper, you can only see what’s out the top left of the hole, that kind of thing.

What that will actually do is be generating a fully focussed (but upside down and back to front) image on the paper of what’s in front of the box, just from the light coming through that pinhole.

That’s why looking through a small hole gives you a more focussed picture. Because it’s only letting a certain point on your retina see a certain point of the view in front, and nothing else. It’s doing just the same as what focussing with a lens would do.

Anonymous 0 Comments

Light and the images you see is coming from many different directions and needs to be focused into one point in your eye to see.
When you have blurry vision, this focus or focal point is slightly off so you are seeing multiple “images” at slightly the wrong place, this is what makes things look blurry.

When you look through a pinhole or small hole, a lot of those extra images are being blocked from reaching your eye so you don’t get as much blurriness. Less light is reaching your eye though so your vision is darker but sharper.

Anonymous 0 Comments

It’s the same reason as a pinhole camera works. Also the same as why a smaller aperture on a normal camera lens helps focus.

https://electronics.howstuffworks.com/question131.htm

So that’s probably the easiest way to understand it.

Anonymous 0 Comments

When looking through very small hole , we cut light refraction from periphery of human lens. Only Light is passed through center of lens , such light don’t passing through center of lens (also known as Nodal point ) don’t show refraction (deviation ) hence image nia formed in retina (to be precise macula , to be more precise fovea ) .

Hope it answers the question

Anonymous 0 Comments

Most people are just telling you to look up something online, completely missing the fricking point of the sub.

The reason things are blurry is because your eye lens is too strong (or too weak) to focus the light where it’s meant to be for a clear image.
Light that hits a lens strait on is not “refracted” at a different angle. So it does not matter if the lens is the right “strength” to focus the light. It passes strait through regardless.

Making a small hole limits it so that the only light bouncing off the object to reach your eye is the light going strait. Ie blocks all light not traveling strait through the centre of the lens.

Therefor you can see

The only thing that limits it is how much light can pass through the hole to be able to actually “see” it (which is why we have eyes bigger than pinholes in the first place with the lens as a corrective measure)

Anonymous 0 Comments

Yeah, as noted, this is the pinhole effect. It does not focus the light *at all.* But it makes the depth of field, or the “in focus” range so big, it significantly improves the image. They won’t let me post an image, but if you an image search for “pinhole effect”, all will be made clear.

I’m an optometrist, and also used to work as a photographer.

And it has little or no effect on field of view.

Anonymous 0 Comments

After retina surgeries, I’ve done so many pin hole tests and I never knew the answer. Thanks for asking!

Anonymous 0 Comments

Light from a point in the scene only has one possible path to the retina and light from no other point in the scene can hit the same point on the retina. The image is therefore sharp.