Understanding Your Contact Lens Prescription

In February 2004, legislation went into effect giving all U.S. consumers the right to a copy of their contact lens prescription (before then, only consumers in certain states were entitled to their Rx). Contact lens wearers in all 50 states now have the option of buying contact lenses from their eyecare practitioner (ECP) — a catch-all term for optometrists, ophthalmologists and opticians — or shopping around at various optical chains, warehouse clubs, and Internet sites. Click here for the text of the legislation.

It's important to remember that this law doesn't eliminate ECPs from the process of fitting and prescribing contacts. In the United States, contact lenses are a prescription item, just like medicines. And even if you already have an eyeglass prescription, you need a contact lens prescription that contains additional information.

The 2004 law pertains to buying the lenses themselves, after you've been fitted — and especially the continual supply of replacement contact lenses you'll need if you wear disposable contacts.

A contact lens is a medical device. If it's not properly prescribed, you may not see well. More importantly, a poorly fitting lens — or one made from a material not well-suited to your eyes — could result in discomfort, inflammation, swelling, abrasion, or another problem that could, in rare cases, result in permanent eye tissue damage.

That, and the risk of infection, are also why it's unwise to share contact lenses with other wearers.

Throughout the United States, you can be fitted for contact lenses by an optometrist or ophthalmologist. In some states, opticians also can be certified to fit contact lenses.

By law contact lens prescriptions are valid for a minimum of one year, or the minimum required by state law, whichever is greater.

When your prescription expires, you won't be able to buy more lenses until you get an updated prescription. This will probably involve a checkup by your ECP to be certain that contact lenses aren't adversely affecting your eyes.

"Just because your eyes feel good and your contact lenses seem to be working well does not mean your eye health is O.K.," says Charles Slonim, MD, an ophthalmologist in Tampa. "You may be having microscopic problems that can be seen only with a slit lamp [a type of microscope used during an eye exam]."

Dr. Slonim says that about 10 percent of the time when he sees a patient during a follow-up visit, he notices something that could become a problem if not taken care of immediately.

Remember, if you're diagnosed with a lens-related problem, it's unlikely that you'll have to permanently discontinue wearing contacts. Chances are you'll simply need a different size, material or design of lens.
 

Eye doctors use standard terms, abbreviations and measurements to write contact lens prescriptions. It can look like a secret code at first, but it's really quite simple to decipher.

Below is an example contact lens prescription. Place your cursor over each element, and it will be explained on the right:

In addition to the above information, your prescription may note how often your contact lenses must be replaced (once a month, every two weeks, once a week, daily, etc.). Or you may be instructed verbally, during your exam. Often the lens brand includes this information (e.g., Ophtha-Lens One-Week), but the real judge is your eyecare practitioner, who knows which replacement option is best for your eyes and lifestyle.