Why measurements matter more here than with most other online purchases

If you want to buy glasses online, picking a frame and a colour is not enough. Unlike most other products, how well a pair of glasses actually works depends on several personal measurements that no product photo can show. If one of these measurements is missing or copied down wrongly, even technically perfect lenses end up sitting wrongly in the frame, and your vision stays uncomfortable or blurred despite the correct prescription.

This article sets out which details you need, which lens options cost extra and what to look out for when you order, whichever provider you end up buying from.

Your current prescription: the basis for every order

For any pair of prescription glasses, you need up-to-date details of your prescription, usually from an eye test. These details go out of date over time, because your eyesight can change over the years, so a much older prescription is no longer reliable. If you are not sure whether the figures you have are still current, have them checked again before a larger order rather than relying on a prescription that is several years old.

Pupillary distance: the measurement most often missing online

Besides the prescription, every pair of glasses needs your pupillary distance, often shortened to PD. This is the distance between the pupils of your two eyes, and it ensures that the optical centre of each lens really sits in front of the pupil. This figure is not automatically included on every prescription, so you may need to have it measured separately or ask for it. A wrong or missing pupillary distance can cause noticeable distortion or headaches with stronger prescriptions, even if the lens strength itself is correct.

Frame measurements: why an existing pair helps as a guide

Apart from your personal details, a well-fitting frame has its own measurements: the width of the lenses, the distance between the lenses across the bridge of the nose and the length of the arms to the ear. These three numbers are often printed in small type on the inside of the arm of a pair of glasses you already own. If you have no pair to go by, comparing the measurements given on the order page with similar models you already know can help you roughly judge whether a frame is likely to be too small or too large.

Lens options: where the real extra cost comes from

The price of a frame is often only part of the total cost, because extra lens options frequently add more to the bill than the frame itself. These include an anti-reflective coating against distracting reflections, a blue light filter if you spend a lot of time at screens, a thinner lens material for stronger prescriptions and varifocal (progressive) lenses that combine several viewing zones in a single lens. Each of these options is usually charged separately, which is why it is worth looking at the final total, not just the frame price shown first.

A worked example

Say a frame costs 39 euros. Basic lenses with your prescription are included, an anti-reflective coating costs an extra 19 euros, a blue light filter another 15 euros, and because your prescription is fairly strong, the provider recommends a thinner lens material for an extra 25 euros. In the end, you pay 98 euros for the complete pair of glasses instead of the 39 euros first advertised for the frame alone. That is not a hidden cost trick, but the usual price structure for ordering glasses. Even so, it is worth working out the full total once before you order instead of going by the frame price alone.

Trying on and returns: what you can rely on

For online purchases within the EU, there is generally a 14-day right of withdrawal. This is an EU rule; outside the EU, for example in the UK, the US or Canada, your own country's rules apply. With glasses whose lenses are made to your personal prescription, however, returns may be restricted, which is why many providers set out their own conditions for them. Some providers also let you have several frames sent to try on before you place the actual order with the right lenses. Whether and in what form such a home trial is offered varies from provider to provider, so it is always worth checking the delivery and returns conditions before you order.

• Check that your prescription is still up to date before using it for an order.
• Find out your pupillary distance if it is not already noted on your prescription.
• Measure a pair you already own for comparison of lens width, bridge width and arm length.
• Add all the lens options you want to the frame price before you judge the final total.

Frame material and why it affects the fit

Besides the measurements themselves, the material of the frame also affects how a pair of glasses ends up sitting on your face. Plastic frames can often only be readjusted with some effort, while metal frames can frequently be bent slightly to adapt the arms or nose pads to your face. If you already know that a previous pair pinched or slipped in certain places, factor that into your choice of material rather than only noticing it after delivery, because readjusting glasses you ordered online is not as straightforward as it is with an optician in person.

Before you order

How the right of withdrawal for online purchases within the EU works in detail is explained in the article The right of withdrawal for online purchases: 14 days, when it starts and exceptions. Who pays for a return is covered in the article Returns and return shipping costs. Clothing has a very similar fit problem to glasses frames, which you can read about in the article Buying fashion online: clothing sizes, fit and why returns happen. You can find current deals under categories, and general answers about shopping under Frequently asked questions.

Frequently asked questions

What happens if the pupillary distance is given incorrectly?

The optical centre of the lenses will not sit correctly in front of your pupils, which can lead to distortion or headaches, especially with stronger prescriptions, even if the actual lens strength is right.

Is a prescription that is several years old good enough for an order?

Not reliably, because your eyesight can change over the years. With an older prescription, it is worth having your eyes checked again before using it for a new pair of glasses.

Why do finished glasses often cost much more than the advertised frame?

Because extra lens options, such as an anti-reflective coating, a blue light filter or thinner material, are usually charged separately. The price shown first often only covers the frame with the most basic lenses.

Can I simply send back glasses ordered online if they do not fit?

Within the EU, the 14-day right of withdrawal generally applies to online orders; outside the EU, your own country's rules decide. With lenses made to your individual prescription, it may be restricted, so it is worth reading the provider's returns conditions before you order. They will also tell you who pays for return shipping.