The simple answer to this question is absolutely not. But why is that the case? Keep reading to learn more.
In the United States, contact lenses are classified as medical devices, and you cannot order them without a prescription. Contact lens sellers are required by law to check and make sure that you have a valid prescription written by a licensed optometrist or ophthalmologist.
An expired contact lens prescription cannot be used to order contacts either, and these rules apply to both physical and online retailers.
A glasses prescription is insufficient for buying contact lenses. This is because, even if your vision hasn’t changed, glasses sit a short distance in front of the eyes, while contact lenses sit directly on the surface of the eyes.
While this might seem like a very minor difference, when it comes to lenses, it actually affects a great deal, and you are likely to have a different prescription power for glasses and contacts, meaning that if you did use a glasses prescription for contact lenses, they would not be at the proper strength for what you need.
Contact lens prescriptions include additional elements that are not included in a prescription for eyeglasses. During a contact lens exam the eye doctor will take these measurements which are not taken for eyeglasses.
During a contact lens exam the eye doctor takes a measurement of your base curve which is the curvature of the back surface of the contact lens. The eye doctor measures this to ensure that the contact lens matches the shape of your cornea. Without a base curve measurement that matches your eyes your contact lenses may be too loose or too tight.
Another important measurement used for fitting contact lenses is determining the proper diameter of the lens. The eye doctor will match the lens to your eye so that the fit is not too tight or loose. In addition the diameter may be adjusted based on understanding the background of the patient's history. For example your eye doctor may recommend a wider diameter contact lens in order to reduce sensitivity and stop the lens from moving as much. These kinds of adjustments are often made for patients with corneal scarring, sensitivity, dry eye disease, or an athlete.
Now that we’ve established that yes, you do need a contact lens prescription, the next question is how do you get one?
A contact lens prescription must be obtained from an optometrist or an ophthalmologist, following both an eye exam and a contact lens fitting.
The eye exam, as you might expect, determines whether you are, for example, farsighted or nearsighted, and just how much correction you need.
The contact lens exam and fitting process is just as important.
A contact lens exam and fitting is a vital part of the process of getting contact lenses. During your first fitting appointment, you will be asked about your lifestyle and how you plan to wear your lenses in addition to discussing your eye health history. This is so they have as complete an understanding of both your eyes and your activity level to decide what sort of lenses to recommend.
During the course of the fitting, you will have a keratometry reading (to determine the base curve and diameter of the lenses you’ll need), as well as an assessment of the tear film. The latter is to ensure that your eyes produce enough moisture for you to safely and comfortably wear contact lenses.
Following this, you’ll be given trial lenses. You will use these to practice putting them in and taking them out safely, make sure they sit well on your eyes, and ensure that you can see well while they are on.
You will use these at home for a couple days before returning for a follow-up appointment, at which the optometrist will again check your eye health. They will then make any necessary adjustments to their determinations from the previous appointment, then provide you with your prescription.
All of this ensures you get the lenses that will provide you with the best possible results.
While these are the general guidelines of a contact lens exam, more advanced contact lenses such as contact lenses for myopia management and scleral lenses for keratoconus may require additional follow up appointments to assess how the patient is adapting to their contact lenses.