How does squinting work?

Light passing through a misshapen lens misses the focal point. The farther the light rays are from the center of the lens, the more they are diverted from the focal point. Squinting reduces the amount of peripheral light entering the eye. Limiting the rays of light that come in through the pupil allows rays to pass closer to the center of the lens creating a more focused image. Of course squinting also constricts the visual field and decreases the brightness of the image.