Contact lenses are an option for people who need a prescription for better vision but prefer an alternative to eyeglasses. However, in order for contact lenses fit well, they need to provide the right vision correction -- and they need to be fitted to your eye shape. So wearing lenses from an outdated prescription, or wearing lenses that are not fitted to your eyes, can lead to discomfort, blurry vision, and increase the chance of eye damage and infection.
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Since contacts are meant to improve vision, wearing lenses with an incorrect or outdated prescription will typically cause vision impairment, including blurry vision. Sometimes eye strain and headaches are related to wearing the wrong prescription lenses. In some cases, a person with poor vision may notice a slight improvement in vision, even with the incorrect prescription. However, vision will not be clear unless the prescription is correct. However, wearing the wrong prescription lenses will not permanently worsen vision.
The cornea, which is the thin, clear and dome-shaped surface that covers the front of your eye, needs to be professionally measured so that contact lenses will properly fit the eyes. Wearing the wrong prescription contact lens may feel uncomfortable, and ill-fitting lenses may even scratch the eye’s surface. If the lens fits too tightly over the cornea, it may not receive nourishment from the tears that protectively coat the eye. This can lead to irritation and blurry vision. Extended use of lenses with an improper fit may eventually lead to a corneal infection.
Corneal ulcers may also result from wearing an incorrect prescription. A corneal ulcer will typically cause severe eye pain, tearing and light sensitivity, and might even lead to infection. If a person experiences these symptoms, she should stop wearing the contact lenses and seek an evaluation from an eye doctor. The doctor may prescribe one or more eye drops to treat the infection. Without treatment, permanent scarring of the cornea can occur, which may impair vision long term.
Contact lenses that are not properly prescribed and fitted by an eye doctor may not work well, and can damage your eyes. Even decorative contact lenses, which are worn to change the color or look of the eyes, require a professional fitting by an eye doctor. Wearing improperly fitted contact lenses can lead to blurry vision, discomfort and increase the risk of infection, injury, swelling and vision loss. It's important to see your eye doctor every 1 or 2 years to check for proper prescription and fit, and to monitor the health of your eyes.
Reviewed by Kay Peck, MPH RD