The difference between a contact lens prescriptions and glasses prescription

Many people who wear glasses also choose to use contact lenses. If you’re considering including them in your eye health regime, you’d be forgiven for thinking you can simply order the same prescription as you have for your regular eyewear. However, the two are often different and it’s essential to get both right. Incorrect prescriptions can lead to multiple complications including blurry vision, headaches and eye strain. In the long term, they can even accelerate vision deterioration permanently.

Our guide outlines the key prescription differences when it comes to glasses and contact lenses, ensuring your vision and eye health are optimised, whichever solution you’re using.  

Main differences between contact lens prescriptions and glasses prescriptions

Consider the positioning of both glasses and contact lenses. Glasses sit on your nose, typically around 12mm away from your eyes, although every individual has their own preference when it comes to style and comfort. In contrast, contact lenses sit directly on the surface of your eye. As such, different sets of information are needed for each to achieve the best vision correction.

Glasses prescriptions

A glasses prescription includes a selection of different numbers and abbreviations that quantify your range of sight. These indicate the percentage of correction needed for each eye to improve the quality of your vision, and are known as diopters. You will also notice a plus or minus sign against these numbers - this indicates whether the eye is short-sighted or long-sighted. What you likely won’t see on a glasses prescription is an indication of the lens shape. Glasses lenses have a standard curve that accommodates most angles of sight but still leaves a small area (to the far right and left of each eye) that isn’t covered.

Contact lens prescriptions

Contact lens prescriptions have additional information to ensure the new lenses fit your eyes more effectively, including:

  • BC or Base Curve - The curvature of the back surface of the lenses. This is used to ensure the contact lenses lie flat against the eye, once inserted.
  • DIA or Diameter - This is the full width of the required contact lens, ensuring it fits over your cornea.
Axis value

If you have astigmatism (an imperfection in the curvature of the cornea or lens), you will have an axis value of 1-180 as part of your prescription. This will be different for your glasses and contact lenses prescriptions, as the number must reflect how close the lens is to your eye.

In order to use contact lenses properly, we highly recommend you have a full eye examination and contact lens fitting appointment every year. As expert opticians in London, we at The Eye Establishment can provide an extensive review, identifying any changes to your glasses prescription and reviewing the fit of your contact lenses. Any necessary alterations can be made while our professional opticians assess the eye to ensure everything is healthy.

As an independent optician in Kensington, we are dedicated to supporting all of our customers with their continued eye health. Our expert team is on hand to answer any questions, while our extensive range of leading glasses brands ensures you’ll find a pair to suit your needs perfectly. If you’re looking for ‘independent opticians near me’ for an eye test or lens check, book an appointment today.