How Do Astigmatism Contacts Work?

Determining Astigmatism Level

Astigmatism is a condition in which the cornea is irregularly shaped and therefore unable to properly focus light rays, creating vision that is slightly blurry, even when corrected with typical glasses or contacts. Patients may describe their vision as fuzzy or lacking crispness. Therefore, contacts to correct astigmatism often not only correct vision, they also must correct the problems with the shape of the eye.

Contact lenses to correct astigmatism are known as toric contact lenses. These lenses not only correct the vision in the eye, they also correct the eye's shape. To begin, an ophthalmologist measures the degree to which a person's retina is misshapen. This curvature is then translated into a recommendations for a contact lens, which is individualized for each person.

Contact Placement

Most contact lenses can move on the eye from side to side and the person wearing them can still see. For this reason, many patients with astigmatism could not wear contact lenses because toric lenses had not yet been created.

Since the toric lens must sit directly on the cornea enough to reshape it, the lens is place on the eye and must stay directly on the eye in order to be effective. For this reason, the toric lenses are weighted on the bottom portion to better hold the contact to the eye.

Contact Curvature

Patients that require contacts to correct astigmatism as well as another vision condition, such as hyperopia (farsightedness) or myopia (nearsightedness), will have two curvatures to their toric contacts. The first will be to correct the cornea's shape and the second will be to correct the vision problem. This is why the toric lens must remain in position at all times in order to ensure correct vision.

Dependent upon the level of nearsightedness or farsightedness, it may be possible for some contact lens wearers to wear disposable contacts. Those with higher degrees of vision difficulties often must wear non-disposable lenses. Another option for toric lenses is the silicone hydrogel lens. Because most contacts rely on motion to provide oxygen to the cornea and toric lenses necessitate stationary motion, silicone hydrogels allow oxygen to naturally pass through the lens. This allows the wearer to keep the contacts on the eye for up to 30 days at a time while the eye receives enough oxygen.