Astigmatism and Contact Lenses

Astigmatism is a commonly heard term, but few people know exactly what it is. Like near-sightedness (myopia) and far-sightedness (hyperopia), astigmatism is another condition that is usually correctable with glasses or contact lenses.

Astigmatism is typically a result of the cornea (the clear dome-shaped part that covers the colored part of the eye) being shaped irregularly rather than round (or cylindrically). Because of this variation in the curve, when light enters the eye, it focuses in more than one place. To correct for this, we put two powers in the glasses or contact lenses in order to allow all the entering light to focus in one spot to give the best, clearest vision possible. This type of lens is known as a “toric” lens, i.e. the lens surface is a combination of a sphere and a cylinder.

In the past, patients with astigmatism were more difficult to fit with contact lenses. But with today’s technology, most people can successfully be fit into soft toric lenses or rigid gas permeable (RGP) lenses. With soft lenses, the type of lens is dependent on the amount of astigmatism. We have disposable soft toric lenses that correct for low to moderate amounts of astigmatism, as well as custom toric lenses that correct for higher amounts of astigmatism. RGP lenses, the newer generation of hard contact lenses, do an excellent job at correcting for astigmatism, too. For lower amounts of astigmatism, often standard lens designs can be used. If you have a higher degree of astigmatism, you may need a design called a bitoric lens.

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