Clearing Up the Difference Between a Contact Lens and Eyeglass Prescription

Think you need only one prescription for both your eyeglasses and contact lenses? Think again! Prescriptions for glasses and contacts have important differences and are not interchangeable. A new article on AllAboutVision.com – Are Contact Lens and Eyeglass Prescriptions the Same? – explains how the prescriptions are different, and why you cannot use an eyeglass prescription to buy contact lenses.

Because a contact lens rests directly on the surface of the eye, a prescription for contacts must include parameters that determine the fit of the lenses, including the base curve and diameter of the lenses, which are determined by the shape and size of the front of your eye. Also, the brand name or lens material must be specified on a contact lens prescription.

"You can obtain a copy of your glasses prescription at the conclusion of a comprehensive eye exam, but a contact lens fitting must be performed before your eye doctor can issue a contact lens prescription," says Gary Heiting, OD, AllAboutVision.com senior editor. "Or, if you already wear contacts and your eye doctor has access to your current contact lens prescription, he or she can update the prescription after adequately evaluating the fit of your current lenses."

Also, the lens powers on your contact lens prescription may differ from those on your glasses prescription, depending on the degree of your refractive error and the type of contact lenses prescribed, says Dr. Heiting.

Interactive diagrams in the AllAboutVision.com article show the anatomy of contact lens and eyeglass prescriptions. The diagrams explain terms such as sphere, cylinder, axis, add and prism, as well as the meaning of common abbreviations used on the prescriptions.

The new article is part of 30 Contact Lens FAQs on AllAboutVision.com.

Online since 2000, AllAboutVision.com is an independent resource providing consumers with hundreds of pages of trustworthy, up-to-date information on vision correction and eye health. The site is a National Gold Sponsor of Optometry Giving Sight and is certified by the Health on the Net Foundation.