Toric Contact Lenses
All that once was true, but not today. Unless you have an especially complex prescription, your astigmatism probably can probably be corrected with soft contacts, and you have many options.
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What Are Toric Contact Lenses?
An eye with astigmatism has different degrees of myopia or hyperopia in different meridians of the eye. A toric contact lens has a special design to accurately correct vision in all meridians of the eye by aligning the appropriate lens power in front of each meridian.
To accomplish this, toric contacts for astigmatism have two features that set them apart from regular ("spherical") contact lenses that correct only nearsightedness or farsightedness:
- Different powers in different meridians of the lens.
- A mechanism that enables the lens to rotate to the proper position so the power meridians of the lens align with the appropriate meridians of the eye for clear vision.
Toric designs are available in both soft contact lenses and rigid gas permeable (RGP or GP) contact lenses. But generally, when people talk about toric contact lenses, they are describing toric soft lenses, which are much more common than toric GP lenses.
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.
Toric Contact Lens Cost
Fitting contact lenses for astigmatism whether they are toric soft lenses or toric GP lenses takes more of your eye care practitioner's time and requires more expertise than fitting spherical contacts.
Consequently, a toric contact lens fitting typically is more expensive than a regular contact lens fitting. The lenses themselves also cost more than spherical lenses.
Options for Mild Astigmatism
If you have a small amount of astigmatism (less than 1.00 diopter), you may be able to wear a regular spherical GP lens or even a spherical soft lens.
How can you see well if there is no power for astigmatism?
Spherical GP lenses can correct mild amounts of astigmatism because they are made of firm plastic and do not conform to the asymmetric shape of the front surface of an astigmatic eye. Instead, GP lenses optically replace the astigmatic curves of the cornea with the spherical front and back surfaces of the lens for sharper vision.
Spherical gas permeable lenses also can correct astigmatism greater than 1.00 diopter (D), but a spherical design typically is less comfortable on eyes with high astigmatism. Toric GP lenses, which have an asymmetric posterior surface, are more comfortable on eyes with higher amounts of corneal astigmatism because the back surface of the lens conforms more closely to the shape of the astigmatic eye.
Even some soft contact lenses have enough thickness and rigidity to "mask" small amounts of astigmatism and provide acceptable vision in cases of astigmatism less than 1.00 D. Patient satisfaction with this approach depends on the wearer's expectations and his or her willingness to sacrifice some clarity of vision for the comfort and economy of wearing a spherical soft lens.
Special aspheric soft lenses that are designed to reduce spherical aberration of the eye are another option in cases of mild astigmatism. These aberration-correcting soft lenses might help some people who have astigmatism see better without the necessity of a toric lens.
Soft or RGP Contact Lenses for Astigmatism?
As mentioned above, gas permeable contact lenses retain their shape on the cornea better than soft lenses and tend to provide sharper vision than soft toric lenses.
This degree of difference in visual clarity may not be noticed by some contact lens wearers, but if you're particularly fussy about your vision, you are likely to appreciate it.
Still, most people who need astigmatism correction choose soft toric lenses instead of GP lenses because of the immediate comfort of soft lenses.
Color, Disposable, and Multifocal Toric Choices
Many brands of soft toric lenses are available today, so your eye care 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 soft lenses also are available in many colors that either change or enhance your natural eye color. Some toric colored lenses are disposable, but depending on the color and your prescription, you may have to settle for non-disposable toric lenses with a conventional replacement schedule.
Multifocal torics are available for the correction of astigmatism and presbyopia. These are generally non-disposable as well. There are some soft toric multifocal brands, but often an RGP lens is prescribed in this instance.
Silicone Hydrogel Toric Lenses
A number of toric silicone hydrogel brands are available, including one for 30-day wear. Custom silicone hydrogel lenses can be made-to-order for unusual prescriptions, including those with irregular astigmatism. These lenses usually are designed for a quarterly replacement schedule.
If you have astigmatism and are interested in wearing contact lenses, visit an eye care practitioner who has expertise fitting toric contact lenses to see if you are a good candidate for these lenses and to determine the best toric design for your particular needs.
About the Author: Gary Heiting, OD, is senior editor of AllAboutVision.com. Dr. Heiting has more than 25 years of experience as an eye care provider, health educator and consultant to the eyewear industry. His special interests include contact lenses, nutrition and preventive vision care. Connect with Dr. Heiting via Google+.
[Page updated July 2014]
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