Are Glasses and Contact Prescriptions the Same?

Written By: Adara Ofitserova

Some people wear contacts and eyeglasses, depending on the day and activity. If you have been to the eye doctor and wear both, you likely know they usually give you two separate prescriptions.

Many people wonder if they can switch glasses and contact prescriptions. The answer to this question is no. There are significant differences between glasses and a contact lens prescription.

Contact Lens Prescriptions and Eyeglasses: The Two Are Very Different 

You cannot use an eyeglass prescription to fill your contacts and vice versa. Since your eyes do not change whether you are wearing prescription contacts or eyeglasses, why would you need two prescriptions?

One of the key reasons you need two prescriptions is because contact lenses sit directly on your eyes, while eyeglass lenses are about 12 millimeters away. Most people consider this a minute difference, but the spacing is enough to change your prescription needs slightly.

For most people who wear both glasses and contact lenses, the prescription for contact lenses would be too weak if placed in their glasses. Another key difference is that contacts are designed to fit the curvatures of your eyes with the lens material. A contact lens prescription has additional specifications that a glasses prescription does not, including the following:

Lens Diameter 

The lens diameter is the overall size of the contact lens. Without the right size, your soft contact lenses would slip around on your eyes.

Base Curve 

The base curve is essential for the fit and your ability to see correctly. The base curve measures the curvature of the contact lens’ back surface.

The base curve measurement is one of the most essential for ensuring a contact lens fits. Contact lenses will not allow you to see correctly without the right lens curvature.

Contact Lenses Brand 

While you will never see a brand listed on an eyeglasses prescription, you will when it comes to contact lenses. Different prescriptions require lens brand because of the differing levels of breathability.

The prescription should always clearly state the lens’ fit lens brand. You need a high level of breathability, especially if you wear long-wear contact lenses.

Refractive Errors Are Common 

With this condition, your eyes cannot bend light correctly. Instead of being able to see with clarity, these abnormalities can cause blurriness.

Some of these errors include nearsightedness, farsightedness, and astigmatism. With the right glasses prescription, you can get the astigmatism correction you need so you can see clearly. With glasses and contact lenses, you can see better.
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Eye Exams Are Critical For Getting a Contact Lens Prescription 

Before getting a contact lens or glasses prescription, you will need to have an eye exam carried out by your doctor on your eye lens. The eye doctor will need to test your eyes in various ways and take measurements to ensure you get the right level of vision correction, just like with your glasses prescriptions.

There are different lens materials. While each one may only offer minute differences, this seemingly minor difference requires a special prescription to experience more natural vision without seeing a blurred image. You will need a yearly eye examination to update your glasses and contact lens prescriptions.

How to Decipher the Symbols and Words on Your Prescription 

You have just been to the eye doctor and obtained your contact lens prescription and glasses prescription, but what do those symbols and words mean? The following are some of the abbreviations you may see on your glasses prescription or contact lens prescription and their meanings:

  • SPH – This abbreviation stands for sphere. This stands for the amount of lens measured in diopters and is essential information for when you get contact lenses filled.
  • PD – PD is the distance from the center of your pupils.
  • CYL – CYL stands for cylinder. CYL will indicate the power you need for your glasses prescription to correct astigmatism.
  • AXIS – AXIS denotes the orientation of your astigmatism.
  • OD – OD stands for Oculus Dexter and refers to your right eye.
  • OS – OS stands for Oculus Sinister and refers to your left eye.
  • A – indicates the patient is nearsighted.
  • A + indicates the patient is farsighted.
  • The farther from zero, the stronger your glasses prescriptions.

FAQ About Contact Lenses and Eyeglasses Prescriptions 

Here are some frequently asked questions about contact lenses and eyeglasses prescriptions.

Can You Convert a Contact Prescription to Eyeglasses? 

You cannot convert them because extra specifications are required for multifocal lenses, so you need a particular contact lens exam.

Will My Contact Lens Prescription Be the Same as My Eyeglasses?

A glasses prescription and a contacts prescription are entirely different. You need a different prescription because the contact lens material goes directly on your eye’s surface. The lens power will be too weak for your refractive error.

When Do Contact Prescription Expires? 

Depending on your doctor, contacts prescriptions will expire after one to two years. When purchasing contacts, you should also be aware of the oxygen permeability expiration date of the contacts.

Final Thoughts 

You cannot interchange glasses prescriptions with a contact lens one for vision correction. Your natural lens needs an appropriate fit for contacts and progressive lenses.

Published on: April 7, 2023
Last Updated: April 7, 2023

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