Can you convert a glasses prescription to a contact lens prescription?

Thursday, 04 April 2019
Can you convert a glasses prescription to a contact lens prescription?

A common query for contact lens wearers is whether you can convert your glasses prescription into a contact lens prescription. We’ve got the answer for you.

Both contact lenses and glasses correct common refractive errors such as myopia (short-sightedness), hyperopia (long-sightedness), astigmatism which requires toric lenses and presbyopia which requires multifocal lenses. Although your contact lens and glasses prescription may look similar, it does not mean they will give you the same visual acuity if you try to convert one to the other.

 

Can you convert glasses prescription to contact lenses?

No – you cannot directly convert a glasses prescription to a contact lens prescription. Equally, you cannot convert a contact lens prescription to a glasses prescription.


Can I use my glasses prescription for contact lenses?

The simple answer to this question is no – you cannot and should not use your glasses prescription to try to calculate your contact lens prescription. It should also be noted that not everyone who needs glasses can also wear contact lenses, it is important that you are examined separately. Some people have sensitive corneas or other eye related complications and will simply never be able to adapt to wearing lenses.


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Is a glasses prescription different to a contact lens prescription?

Yes, a glasses prescription is different to a contact lens prescription. Glasses sit slightly away from your eyes and contact lenses sit directly over your eye, so two different tests and measurements are required. Depending on the refractive error and the strength of lens required to correct it and the type of contact lens you need, the parameters specified on your glasses prescription may be significantly different from those on your contact lenses prescription.

Contact lenses prescriptions include certain specifications that are not part of a glasses prescription, these include:

Base curve: the base curve measures the curvature of the lens, is determined by the actual shape of your eye and produces the right lens fitting.

Diameter: the lens diameter specifies the overall size of the lens and along with the base curve, how the lens fits on the eye.

Lens material: in days gone by, glasses were made from actual glass, nowadays, most glasses are now made of a lightweight plastic. Contact lenses on the other hand, are made from a range of hydrogels. These are split into hydrogel or silicone hydrogel contacts. How each lens fits and feels depends on each individual wearer’s eyes. Those with sensitive or dry eyes generally do better with silicone hydrogel lenses as they allow a greater level of oxygen and hydration in the eye.

A glasses prescription contains a sphere indicating the lenses power, a cylinder indicating strength of any astigmatism and an axis showing the orientation of the cylinder. Multifocal lenses require an ‘add which indicates additional positive power that enable the eyes to focus for close work.

A contact lens prescription may also include an axis if it is a toric lens for astigmatism or an add if it is a multifocal lens, these are the only two measurements that can be found on both contact lenses and glasses prescriptions.


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How can I order contact lenses online?

You can order contact lenses online, but you must have a valid prescription from an optician. Once you have your prescription, you may order you lenses anywhere you like and it is cheaper to order your contact lenses online.

It is illegal for your optician to withhold your contact lens prescription from you.

 

How do you read a contact prescription?

You can read our comprehensive guide on how to read a contact lens prescription here.

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