Yes, actually squinting can improve your vision. Squinting slightly changes the eye's shape, and hence its optical properties. It also forces the light through the center of the lens, which has a more precise focus than the edges. It is a quick method to assess best corrected vision. By looking through a pinhole, the refractive errors of the peripheral cornea and crystalline lens of the eye are significantly reduced or eliminated, and acuity simulates that with proper glasses in place. Squinting is not a long-term solution for improved vision. It markedly constricts the visual field and reduces total illumination.