Toric Contact Lenses for Astigmatism
Toric contact lenses are made from the same materials as regular (“spherical”) contact lenses, so they can be either soft or RGP. The difference is in the design of the lens.
Toric lenses have two powers in them, created with curvatures at different angles (one for astigmatism, the other for either myopia or hyperopia). There’s also a mechanism to keep the contact lens relatively stable on the eye when you blink or look around. To provide crisp vision, toric contact lenses cannot rotate on your eye.
matism, between zero and 1.00 diopter (either +1.00 or -1.00), you may be able to wear a regular spherical RGP or even a spherical soft lens.
How can you see well if there is no power for astigmatism? With RGPs, the lenses’ rigidity can help mask a need for an astigmatic correction, because your cornea will to some degree conform to the shape of the lens. With soft contact lenses, some eye care professionals choose to fit you with a higher powered spherical soft lens to mask a small astigmatic correction. The results of this technique vary from one patient to the next, which is why the fitting process may take some trial and error by both the doctor and the patient.
Also, some lenses are available that may reduce the spherical aberration of your eye (that exists along with the myopia or hyperopia, and astigmatism). This type of lens may help some people who have astigmatism to see better without the necessity of a toric lens.
Spherical lenses have the same power all around the lens, so it doesn’t matter if the lens rotates on your eye. Toric lenses have two different powers in the lens, so they must remain in position for best visual acuity. Some toric lenses are heavier (ballasted) at the bottom to keep from rotating.
A small percentage of patients will find that they prefer RGPs over soft contacts. Because rigid lenses retain their shape on the cornea better than soft lenses, they tend to provide crisper vision to people who have astigmatism. This degree of difference in crispness is not noticeable for most contact lens wearers, but if you’re particularly fussy about your vision, you may appreciate it.
Many brands of soft toric lenses are available today, so your eyecare practitioner can choose the brand with the best characteristics for your particular eyes. Torics are available as frequent replacement, disposable and even daily disposable lenses. Toric silicone hydrogel lenses for 30-day wear are also available.