Glasses Prescription vs. Contact Lens Prescription
Have you ever wondered why your glasses prescription is different from your contact lens prescription?
Or if you’ve never noticed the difference, have you ever thought that you could just use your glasses prescription to get contact lenses?
Well, we’re here to let you know that your glasses prescription and contact lens prescription are not the same thing. Because glasses are positioned approximately 12 mm from the eyes while contact lenses rest directly on the surface of the eyes, this causes a discrepancy on the effective optics of the lens.
Consequently, using a glasses prescription to get contact lenses can cause eye strain and headaches due to the difference in power.
Thus, it is important to have a contact lens exam in addition to the regular comprehensive eye exam performed by your optometrist.
These two exams are separate and different, as a contact lens exam also includes a fitting evaluation and follow-up.
The contact lens exam
Even though there are multiple calculators and charts available online to convert your glasses prescription to a contact lens prescription, the contact lens exam is crucial to ensure that the right type of contact lens is chosen for you based on the unique features of your eyes.
The prescription is definitely not the only factor when it comes to choosing contact lenses. Contact lenses have additional specifications that glasses do not, such as base curve, diameter, material, and modality.
The base curve, or back curvature of the lens, helps the contact lens fit properly on your cornea, which can be flatter or steeper than others.
The diameter of the lens is important for lens centration and comfort; the wrong diameter can cause irritation and even abrasions.
The dryness of your eyes can help determine the appropriate water content of soft contact lenses, which are generally made of flexible, water-loving plastics called hydrogels.
In addition, the best modality for your eyes, whether they be daily disposable, 2-week replacement, or monthly replacement contact lenses, may differ from that of someone else based on your eyes and lifestyle.
As a result, changing brands or even just one of the aforementioned factors within a brand requires a contact lens exam by an optometrist. This even applies for plano, or “non-prescription,” colored contact lenses.
Visit your optometrist
Because contact lenses are a medical device, categorized as such by the FDA, they do require an eyecare professional to perform a contact lens exam, even if you only wish to obtain your prescription.
The use of improperly fitting contact lenses puts you at risk for infection, ulcers, and other complications. So the next time you want to order contact lenses, remember to see your local optometrist!
We highly encourage you to not use your glasses prescription as your contact lens prescription since the right contact lenses for you is dependent on so much more than just the power of the lenses.
Where is Insight Vision Center Optometry?
Serving the communities of Costa Mesa, Irvine, Newport Beach, Tustin, Santa Ana, Huntington Beach, and Fountain Valley. Schedule a visit with Dr. Valerie Lam or Dr. Thanh Mai to learn more. Our optometry practice is located in Costa Mesa at 3151 Airway Ave. Suite J2, Costa Mesa, CA 92626. We offer vision therapy and orthokeratology services.
