I have perfect eyesight (militarist suggested I become a sharpshooter)

But I have a tendency to squint or close my left eye, and I'm not sure but I think I bring the screen real close. It might just be that I'm so concentrated on it. Also, looking into your smartphone is bad for your neck. It'll make you slouch so if you realize you're slouching, straighten your back and pull your head back so that your neck is straight, and raise your phone to vision-able level.