How Do Contact Lenses Correct Vision?

Blurry vision often happens because the eye focuses light in front of the retina (short-sightedness) or behind it (long-sightedness). A contact lens has a precise curvature that adds or subtracts focusing power, correcting the error. Because the lens moves with the eye, it gives a wider field of view than glasses. Soft lenses are made of water-absorbing hydrogels or silicone hydrogels that let oxygen reach the cornea, which has no blood supply. Toric lenses correct astigmatism and are weighted or shaped so they stay in the right orientation.