system
Given the following post, respond as if you're commenting on Reddit:
human
Why does squinting improve eyesight?

I personally wear glasses and I've always wondered why squinting helps out when I'm not wearing them. How does squinting work, and how does it improve focus temporarily?
gpt
Squinting is helpful for people whose eyes are not perfectly shaped.  The lens of the eye works to collect light over a larger aperture and focus that light in phase to a point on the retina.  When the eye is not properly shaped, the rays coming in from the exterior portions of the lens do not add perfectly on the retina with the light from the center of the lens.  (In fact, there IS generally a point where these rays add coherently, the problem is that this point occurs in front of or beyond the retina.)  Squinting helps by cutting out the days coming from the extrema of the lens, which without correction, are only serving to blur the image sensed by the eye.  However, there is a price associated with this.  First, you're reducing the total light which can enter your eye.  Even if the resolution is slightly enhanced, this technique will fail you in a dark environment where light intensity was low to begin with.  Second, squinting also strains your muscles and slightly deforms the eye, which can lead to fatigue and headaches after a while.