Contact lens prescriptions are different from spectacle prescriptions although they contain similar information. When you have an exam for contacts, your eye doctor completes a refraction and determines your vision correction. He also measures the surface of your eyes and designs contacts to fit your individual needs. One of the things an eye care practitioner takes into consideration is different contact lens brands. Switching brands is possible but depends on certain criteria.
Contact Lens Fitting
When you have your eye examination for contact lenses, your eye doctor uses a machine called a keratometer. Basic keratometers look similar to telescopes but modern and more technical keratometers are now built into large computerized machines. Both have a chin rest that requires you to look into the machine while your eye doctor measures the surface of your cornea. These measurements, called K-readings, help decide the fit and style of the contact lenses you will be prescribed.
Most eye doctors work with a predetermined number of contact lens styles and manufacturers. There are many different types of lenses and quite a few contact lens companies. Your eye care practitioner will discuss with you the type of lenses you want to wear, either soft, rigid, daily wear, disposable, extended wear, bifocal contacts or even lenses for cosmetic purposes that change eye color.
After determining the style of lens, your doctor will put a trial lens on your eye. This is a contact lens that is part of a set of lenses eye doctors keep in stock to check the fit of a potential contact lens for you. Most doctors keep specific brands in stock and lenses are chosen based on your K-readings and power as well as the type of lens you decided to wear.
After you have your initial exam and fitting, your eye doctor has you come back for several appointments to finalize your prescription. At the final fitting, you are entitled by law to receive a written copy of your contact lens prescription. On the prescription will be written your contact lens power, base curve, diameter, and possibly several other numbers. Most doctors include the brand of contact that they fit you with as well.
Your eye doctor can switch the brand of your current contact lens to something comparable. Because there are so many contact lens companies and lens styles, it is possible to switch lenses to something similar and more economical or to change colors or styles. Most doctors will want to recheck the fit of a new brand to make sure the lenses are fitting correctly.
Some retail optical stores will change the brand of your contact lens based on your written prescription. It is recommended to always have your eye doctor verify the fit of the new brand.