text: Squinting utilizes the muscles that control the lens and your eye. By squinting you are chaging the focal length of the lens and the physical shape of your eyeball. The muscles are actively compensating for the defect in your vision. It is hard to maintain this level of visual acumen and it is very  tiring, hence the reason people wear glasses or contacts. But small defects can be overcome with squinting for brief periods. This is also the school of thoght behind the vision repair methodology. They claim to be able to teach you to use your muscles to correct vision deficiencies. While minor problems can be corrected with rertraining muscles, any substantial changes to the shape of the eye or the position of the lens is too straining for muscles alone and laser surgery, glasses or contacts are needed.