Astigmatism means there is an irregular cornea or internal lens. Adequate correction requires two different prescriptions for each eye. Corneal astigmatism, the most common type, resulting in two different curvatures. Lenticular astigmatism has a round cornea but the internal lens has two different curvatures.
Spherical Contact Lenses: A regular soft contact lens will correct, or mask, up to .50 diopters of cylinder corneal astigmatism. Above .50 diopters the soft lens will be distorted and vision will be blurred. A gas-permeable contact lens, however, can correct up to 3.00 diopters of corneal astigmatism.
Toric Contact Lenses: These lenses have two different powers. We can make toric lenses in soft and gas-permeable contact lenses. The soft lenses begin .75 diopters of cylinder. The toric gas-permeable lenses are usually for corrections over 3.00 diopters of cylinder.