What Happens If You Wear Contacts & Have Astigmatism?

What Happens If You Wear Contacts & Have Astigmatism?

People with astigmatism have one or both eyes that are oval shaped, much like a football. They require special contact lenses to correct their vision. Such lenses reshape the eye’s surface or include additions in the prescription to achieve visual acuity or 20/20 vision.

darkJeanie, Flickr

What is Astigmatism?

Eyes considered normal are spherical in shape; an eye having more of an oval shape and not a sooth cylindrical surface is astigmatic. If you have been diagnosed with astigmatism and wish to wear contacts, you will need Toric lenses or gas permeable lenses.

How the Eye Sees

Eyeball Diagram

To understand how contact lenses work, you should know a little about how the eye sees what it does. Light rays enter the eye through the translucent front cover, the cornea–the eye’s window to the world. The rays travel through the pupil and the crystalline lens, where they are refracted or bent. In the case of a normal eye, the light rays come to rest at one focal point on the retina. The optic nerve transmits a signal to the brain, from which it forms a picture.

In the case of an astigmatic eye, light rays come to rest chaotically, rather than at a single focal point. The result is blurred vision.

Astigmatism & Vision Acuity

For clear vision, an astigmatic eyeball needs a crutch in the form of corrective eyewear. Eyeglasses are sufficient to achieve visual acuity, but contact lens technology has come a long way toward providing an alternative. Special contacts, in effect, reshape the eyeball into a spherical shape, As a result, the astigmatic eye processes light rays as a normal eye does.

Contact lenses for an astigmatic eye are shaped differently than regular contact lenses. RGP lenses are hard and keep their shape giving the illusion the eye is spherical. A regular soft contact lens is the same thickness throughout the lens, but a contact lens for an astigmatic eye is thicker on the bottom side. This is so the contact lens can settle itself in the proper position.

Contact Lens Types for Astigmatism

Advances in technology provide a choice between hard or soft contact lenses:

contact lens_Malkav, Flickr

Rigid gas permeable lenses: hard lenses or soft–maintain their smooth shape and thus effectively compensate for the cornea’s irregularly shaped surface. While providing clearer crisp vision, they are not as comfortable as soft lenses. RGP lenses can be difficult to fit an eye, requiring multiple fittings before the correct fit is found. RGP lenses, however, allow
ore oxygen to flow through the material.

Toric lenses–soft lenses: conform to the eyeball’s shape, fitting snugly over the surface. As they are flexible, they are comfortable to wear, but they are also more prone to tear. Another factor of soft lenses, the material does not allow oxygen to move freely through the material as with RGPs. This will require more frequent replacement. Toric soft contact lenses do not reshape an eye; instead it has multiple prescriptions within the lens–sphere + cylinder + axis–accommodating the eye’s vision. With multiple prescriptions it is important the lens stay in the correct position; settling in the eye correctly and preventing rotation is a factor. This is accomplished by added weight at the bottom of the lens.

Overnight Contacts: Orthokeratology (Ortho-K) is a rigid contact lens that reshapes the eye’s cornea. Typically, you would wear it overnight and remove it in the morning. The lens can temporarily correct moderate astigmatism, freeing you from having to wear it during the day.

How Expensive Are Contacts for Astigmatism

Contact lenses for correcting astigmatism are not like those available for the “normal eye” and are more expensive.

Toric RGP contact lenses have a longer life expectancy than Toric soft contact lenses therefore can be less expensive.

Toric soft contact lenses have a shorter life expectancy that RGPs, therefore are more expensive.

Ortho-K rigid contact lenses are the most expensive due to they’re relatively new in the industry and are the latest in technology advances.

A fitting for Toric contact lenses costs more than a normal contact lens fitting there for can be costly.

Pages: 1 2