University Vision Clinic ~ eye care, glasses, contact lenses, optician, ophthalmologist, optometrist, keratoconus

Astigmatism Contact Lenses

If you asked five different people what astigmatism was, you'd probably get five different answers. Astigmatism, in short, means you need two different prescriptions in each eye, due to an irregular cornea or internal lens. If you know somebody that wears glasses or contact lenses, chances are they have astigmatism.

Here is a cross section of what astigmatism does with light as it enters the eye:

Corneal astigmatism, which is the most common type, means your cornea (the clear membrane in front of your iris and pupil) is not round. You have one curvature radius going horizontally and a different curvature radius going vertically. When light enters the cornea, it is split into two different beams of light, therefore, you need 2 different prescriptions. Lenticular astigmatism means usually the cornea is perfectly round but the internal lens has astigmatism. People with uncorrected astigmatism may notice a doubling or shadowing of objects or words.

Contact Lenses: A regular soft contact lens will correct, or mask, a certain amount of corneal astigmatism, usually up to .50 diopters of cylinder/astigmatism. If you have more than that, the soft lens will be distorted and vision is blurred. A gas-permeable contact lens, however, can correct up to 3.00 diopters of corneal astigmatism.

Toric Contact Lenses: Toric, means astigmatism ground into the contact lens. We can make toric lenses in soft and gas-permeable contact lenses. Toric soft lenses are made starting at .75 diopters of cylinder, if you have .75 or more of cylinder you would need either a toric soft lens or a regular gas-permeable lens. A toric contact lens has two inside curves, resulting in two different powers. Toric gas-permeable lenses are usually needed for people with over 3.00 diopters of cylinder.

University Vision Clinic, Inc
4115 University Way NE #101 Seattle, WA 98105 (206) 633-2000