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

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

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

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 lensessoft 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.

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