Understanding how to read a contact lens prescription
Your contact lens prescription contains specific information to ensure your contact lenses are safe, comfortable and provide excellent vision.
In many countries, your optician must give you a copy of your prescription at the end of your eye test or contact lens fitting — even if you don't ask for it.
If you don't have a contact lens prescription, schedule an appointment with an optician near you.
It is important to know that contacts and glasses prescriptions are not the same. So even if you already have a glasses prescription, you will need a separate contact lens prescription before you can purchase contacts.
If you wear disposable contact lenses, your prescription may include how often your contact lenses should be replaced (once a month, every two weeks, once a week, daily, etc).
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Can you buy contact lenses without a prescription?
In most countries, you must have a valid contact lens prescription written by an optician before you can buy any type of contact lens.
This includes coloured contact lenses or special-effect contact lenses that are designed only to change the appearance of your eyes and do not contain lens power to correct your vision.
Your optician can provide you a copy of your contact lens prescription after a thorough contact lens fitting.
Why do you need a prescription?
It most places in the world, it is illegal to sell contact lenses without a prescription, and for good reason.
A contact lens is a medical device, and a poorly fitted lens — or one made from a material not well-suited to your eyes — can cause distorted vision, discomfort, infection, inflammation, swelling and abrasion. In rare cases, even permanent eye damage and blindness can occur.
Also, you should never share your contact lenses with others, including coloured contacts and special- effects contacts. Sharing contact lenses can cause potentially sight-threatening eye infections and diseases.
When do contact lens prescriptions expire?
Most contact lens prescriptions are valid for at least one year, and the expiration date will be written on your prescription.
When your prescription expires, you won't be able to buy more replacement contact lenses until your optician updates it. This typically will require an eye test to ensure that contact lens wear isn’t affecting the health of your eyes and to see if you require a change in the power of your lenses.
If you are diagnosed with a contact lens-related eye problem, it's unlikely that you'll have to discontinue wearing contacts permanently. In most cases, a change to a different type of lens or different contact lens solution — or a modification of how long you wear your lenses and how frequently you replace them — will solve the problem.
Where can you buy contact lenses?
You typically can use your contact lens prescription to shop for lenses online and elsewhere, and you aren’t required to buy your contact lenses from your optician.
Page updated April 2020