How Does Squinting Help?

By limiting the rays of light that come in through the bottom and top of the pupil, squinting allows rays to pass closer to the center of the lens, thereby creating a more focused image.

Why does squinting improve my vision?

When we squint it creates the same effect as looking through a pinhole. Basically only a small amount of focused central light rays are allowed into the eye. This prevents the unfocused light rays in the periphery from reaching the retina. The result is better vision.

Does squinting affect eye shape?

Your eye lens reflexively changes shape when you squint (Your eyelid doesn't actually do any work). But, the shape change has little effect on the lens, and has little impact on vision compared to the light-reducing effect of a smaller aperture. Of course, the best cure for blurry vision is a pair of glasses.