Normally, I have to wear glasses. However, when I don't put them on, I can still see clearly by doing this: I take both thumbs and forefingers and put them together so there is a tiny hole between them. I look through that.

 

How can that help me see?

By focusing light on the retina?

basically it would be eliminating that which is out of focus, instead of using a lens to correct it. elimination instead of refraction..

Oh... I get it.

Thanks!

basically it would be eliminating that which is out of focus, instead of using a lens to correct it. elimination instead of refraction..

 

To expand on this: a pinhole forces the light to have a one-to-one mapping of object and image - each point on the object has only one ray that goes through the pinhole and forms the image. So there is no way for multiple rays to focus at different depths or places and cause blurring. It's why you can make a pinhole camera. You just lose a lot of light in doing things this way.

 

This is also why smaller apertures have larger depth-of field.

wouldn't that also depend on the level of his estigmatism??

by blocking out most of the visible area, thereby bypassing the estigmatism and having a clearer vision.