Whether or not you knew what you were doing, there's undoubtedly been a time when you found yourself squinting to get a better look at something you otherwise couldn't see. Minute Physics' newest video breaks down this wildly useful little phenomenon.
Basically, there's two different factors at play when scrunching up. First, your eye slightly changes shape, which allows light to focus more accurately on your retina. And second, the amount of light let in goes down, meaning the light itself is hitting your eye from fewer directions. The fewer ways light hits your eye, the more focused your vision.
If this sounds similar to the way a camera lens works, it's because it is. Just like when a camera lens warps and becomes misshapen, when your eyes age and slowly malform, light passing through your eye will deflect differently (read: incorrectly) and miss the focal point. The farther the rays of light are from the centre, the more they deviate from the focal point. So fewer rays of light mean passing closer to the centre of the lens, hitting your focal point just right and producing a crystal clear (or at least close to it) image in your brain. [Minute Physics]