What is astigmatism?
Astigmatism is an optical aberration of the eye that makes it difficult to focus on things at all distances. It occurs when the cornea, the clear covering over your iris and pupil, has a different curvature in different meridians. People with astigmatism have difficulty seeing objects that are not straight ahead and may need to squint or close one eye to see clearly.
Astigmatism is a common vision problem that can affect both children and adults. It occurs in about 33 percent of the population, with men and women being affected equally.
There are two types of astigmatism: Regular astigmatism and irregular astigmatism.
Regular astigmatism is where the cornea is shaped like a football with the different curvatures 90 degrees apart.
Irregular astigmatism occurs when the cornea is shaped more like a rugby ball. The curvatures are more distorted an not along straight axes.
Astigmatism can be corrected with eyeglasses, contact lenses, or surgery in some cases. Regular astigmatism can always be corrected with glasses and contacts for astigmatism. Irregular astigmatism such as in keratoconus needs to be corrected with hard or rigid gas permeable (RGP) contact lenses.
Moderate and severe astigmatism may cause eye strain, squinting, chronic headaches, and poor night vision.
How is astigmatism corrected?
There are a variety of ways to correct astigmatism, depending on the severity.
Eyeglasses and contact lenses are two common options for people with moderate regular astigmatism. Spherical soft contact lenses can be used for individuals with very low amounts of astigmatism.
Standard toric soft contact lenses aren't as effective as rigid gas-permeable contact lenses for correcting large amounts of irregular astigmatism, but they can be a viable option for people with a mild form of the condition.
Can I wear contacts with astigmatism?
Contacts can be worn for almost all types of astigmatism. In fact, certain types of contact lenses will often be the only way the patient will be able to have good vision.
Keratoconus, a condition that creates large amounts of irregular astigmatism can only be corrected with RGP contact lenses.
Types of contact lenses for astigmatism
Contact lenses for astigmatism are designed to correct the visual effects of astigmatism.
There are three types of contacts that people with astigmatism can use: soft toric, rigid gas permeable, and hybrid lenses.
People with very mild astigmatism usually tolerate soft toric lenses well, but rigid gas permeable or hybrid contacts may be able to offer even sharper vision.
Toric soft contact lenses
Toric contact lenses are soft contact lenses that correct for astigmatism. They are made with a silicone hydrogel material that transmits more oxygen to the eye than older generation materials. These lenses are shaped and weighted in a special way so when they are placed on the eye they always orient themselves to the correct position.
Every eye with astigmatism is unique, so it can take some trial and error to find the right lens with the best fit, comfort and visual sharpness.
It generally takes more expertise for the eye doctor to fit a patient for toric contacts than it does for regular spherical contacts. For this reason, a toric contact lens fitting may have a higher cost than a regular contact lens fitting for an eye that has no astigmatism.
Torics are more complex in design, so the cost of replacing them will be higher than most regular contacts.
Rigid gas permeable lenses
Rigid gas permeable contacts for astigmatism are a another popular type of contact lens for astigmatism.
RGP lenses can correct regular or irregular astigmatism. They come a very wide variety of parameters and can also be custom designed on a computer for very exacting fits.
Fitting gas permeable contacts usually takes more time and expertise than fitting regular soft contact lenses (including torics).
Gas permeable lenses should only be prescribed by an eye doctor who is familiar with their use and who can tailor them specifically to the individual's needs.
Hybrid lenses are a type of contact lens that combines the comfort of soft lenses with the sharpness of rigid lenses. These lenses have a RGP material center lens and a soft contact lens skirt surrounding it for comfort.
They are less likely to get dislodged during sports and physical activity, and fit more easily and more comfortably than rigid contact lenses.