Are glasses and contact lens prescriptions the same?

If you wear glasses and are thinking about switching to contact lenses, you might assume you can simply use the same prescription. But glasses and contact lens prescriptions are not interchangeable. While both correct refractive errors like myopia, hyperopia and astigmatism, the way they’re designed and measured is very different.

In this guide, we’ll break down why glasses prescriptions and contact lens prescriptions differ, what each includes and how to safely make the switch to buying contact lenses online with help from an eye care professional.

Why glasses and contact lens prescriptions are different

Glasses sit around 12 millimetres from the eyes, while contact lenses sit directly on the eyeball. This small distance makes a big difference in how the lenses are shaped and what power is needed to give you clear vision. Even if the numbers on both prescriptions seem similar, the fitting and lens type are customized based on where the lens sits.

A contact lens prescription takes into account not just the power needed for vision correction, but also how the lens fits your eye. That’s why you need a separate contact lens exam and fitting to get started safely.

What’s in a contact lens prescription?

In addition to basic vision correction measurements like SPH (sphere), CYL (cylinder) and axis for astigmatism correction, contact lens prescriptions include:

Base curve: A measurement that shows how curved your eye is, specifically, the front surface of your eye, called the cornea. Contact lenses need to match this shape to fit properly. If the base curve is too flat or too steep for your eye, the lens might feel uncomfortable or not stay in place well. So, the base curve helps make sure your lenses sit snugly and comfortably on your eye.

Diameter: This refers to the size of the contact lens, measured in millimetres. It tells us how wide the lens needs to be to properly cover your cornea (the clear front part of your eye). The right diameter helps ensure the lens stays centered and feels comfortable throughout the day.

Lens material and brand: Contact lenses are made from different materials, and some are better suited for people with sensitive eyes or conditions like dry eyes. The brand and material can make a big difference in comfort, eye health, and how well the lens works for you.
Lens type: There are different types of lenses depending on your vision needs
- Single-vision lenses correct general near- or farsightedness.
- Toric lenses are designed for people with astigmatism.
- Multifocal contact lenses help if you have presbyopia, a condition that makes it harder to see things up close as you age. These lenses allow you to see clearly at different near, far, and in between distances.

All of these factors are essential for ensuring your contacts prescription suits your eyes and supports good eye health.

Why you shouldn’t use a glasses prescription for contacts

Using your eyeglasses prescription to order contacts might seem convenient, but it can lead to discomfort, blurry vision or eye strain. Without an accurate base curve or proper fitting, the lens may move around on your eye or block oxygen flow to the cornea. This can cause irritation or even more serious issues over time.

If your prescription includes astigmatism correction, the risk of poor vision or discomfort is even higher. Toric lenses used for astigmatism must align precisely with your eye’s shape to work properly.

The importance of a contact lens fitting

A contact lens fitting is a specialised part of an eye exam. During the fitting, your optometrist or optician will measure your cornea’s curvature, assess tear film quality and test different lens types to see what feels most comfortable. They’ll also check that the lens moves as it should when you blink and that it provides sharp vision.

After your fitting, you’ll receive a valid contact lens prescription, which may differ from your eyeglasses prescription even if your level of short-sightedness or long-sightedness is the same.

Can the prescriptions ever be similar?

Yes, in mild prescriptions for nearsightedness or farsightedness, the difference between a glasses lens and a contact lens may be small. In these cases, the lens power or diopters might only vary slightly. But even then, a proper contact lens exam is needed to check the fit and lens material.

How to convert a glasses prescription to a contact lens prescription

It’s not possible to convert your prescription on your own. The curvature of the lens, your pupillary distance and other measurements all need to be assessed by a trained eye doctor. If you're interested in switching, book a full eye test that includes a contact lens fitting.

Your optometry professional will review your current glasses prescription, examine your eye health and recommend the best contact lens options for your needs, whether that’s single-vision, toric, or multifocal.

Already got your contact lens prescription from the optician? Shop with confidence

If your optician has confirmed your contact lens prescription after a full eye check-up, you are all set to order your contacts. Whether you need prescription lenses for both eyes, or even just your right eye or left eye, we make it easy to find the exact power and lens type you need. From daily disposables to toric lenses for astigmatism and multifocal options for presbyopia, we have the trusted brands and fast delivery to keep your eye care routine on track.

Wearing contact lenses should feel clear and comfortable. If you are ever unsure or experience symptoms like double vision, book a follow-up with your eye care professional.

Shop contact lenses now and enjoy hassle free vision correction, straight to your door.

FREE CONTACT LENSES

FREE CONTACT LENSES

FREE CONTACT LENSES

FREE CONTACT LENSES

Are glasses and contact lens prescriptions the same?

What’s in a contact lens prescription?

The importance of a contact lens fitting

Already got your contact lens prescription from the optician? Shop with confidence

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