Why do contact lenses reduce peripheral distortion compared with eyeglasses?

Contact lenses reduce peripheral distortion compared with eyeglasses primarily because they are positioned directly on the surface of the eye, moving in tandem with the pupil. By resting on a cushion of tears over the cornea, contact lenses eliminate the distance between the corrective lens and the eye that is inherent to eyeglasses.1

This proximity minimizes the prismatic effects and the distortion of image size that often occur when looking through the periphery of thick spectacle lenses. Because eyeglasses are held at a fixed distance from the eye, the wearer's line of sight frequently passes through the lens at an angle, which can introduce astigmatism or other aberrations in the outer parts of the visual field. By conforming to the eye's movement, contact lenses provide a more consistent optical correction across the entire field of vision.12