Are glasses and contact lenses prescriptions the same?

Have you been for an eye test and are now wondering, are glasses and contact lenses prescriptions the same? Although they both work in broadly the same way to correct your vision, the script your optometrist provides may be different for spectacles and contacts.

So, are glasses and contact lenses prescriptions the same?

woman about to insert contact lens
Woman inserting a contact lense

They often differ because contact lenses sit directly on the eye and glasses rest a little further forward, the way that they refract light through the eye is different. This changes the corrective power for each that will be prescribed following an eye test.

Glasses typically sit between 9 and 13 millimeters from the eye and though this may seem a negligible distance, it’s far enough to make a difference compared to contact lenses.

Will I have the same eye test for both glasses and contact lenses?

If you want to wear glasses and contact lenses, you need to have eye examinations for both. During a comprehensive eye test, your visual acuity is tested. This is a measure of the eye’s ability to distinguish shapes and objects at certain distances. The optometrist will also check the health of your eyes and their structure. They will also test for conditions including glaucoma and color blindness.

If you also plan to use contact lenses, the optometrist will determine additional specifications because contacts are designed to precisely fit to your eyes. During a contact lens consultation, the curvature and width of the eyes will be measured. Often referred to as a ‘contact lens fitting’, you will be assessed as to your suitability to wear contacts.

When are prescriptions for glasses and contact lenses the same?

Prescription glasses and contact lenses to correct vision can be different. Though the difference might only seem slight, the readings on your prescription for glasses and contact lenses may not be identical.

The only time they might be the same is if you have a low power spectacle prescription or no need for vision correction. This might apply if you want to wear a pair of specs for fashion reasons or to wear colored contact lenses. If you do wish to wear ‘non-prescription’ contact lenses that have no corrective power, you will still need to visit an optician to have them correctly fitted. Colored contact lenses can’t be sold without a prescription.

Can I use a glasses prescription to get contact lenses?

You will not be able to use a prescription for spectacles to get contact lenses or vice versa. Not everyone who wears glasses will be suitable for contact lenses.

During a contact lens assessment, the optometrist will ask you questions about your lifestyle to work out what type will be best for you. Different types of contact lenses are available and made from different materials. The optometrist will specifically check for eye health issues that might affect contact lens comfort.

You might notice sites online that suggest you can convert a glasses prescription to a contact lens one or the other way round. Such tools are not accurate enough to replace either prescription. There is also specific information on each type of optical prescription that will not be on the other.

You should update your contact lens prescription annually

For most people, it’s recommended that you have an eye test for glasses and one for contact lenses every 12 months. If you’re a glasses wearer who is considering contact lenses (or the other way round), Pritchard Cowburn can advise you on each.

With branches of opticians in Cardigan and Narberth, our friendly and experienced team perform eye tests in Cardigan for locals and visitors alike who choose to wear glasses, contact lenses or both. If you’re still unsure about the answer to ‘are glasses and contact lenses prescriptions the same?’, our experts are more than happy to help.