Guide to Prescription Goggles

Prescription swimming goggles come with specially manufactured lenses which are available in a variety of strengths. The lenses vary depending on what is known as the ‘dioptre scale’: it’s exactly the same as your prescription for standard spectacles. SWANS’ prescription goggles are for myopic correction (short-sightedness) and hypermetropia (long-sightedness, the two most common types of correction.

Swans Prescription Goggles

OK, you’ve decided to buy a pair of SWANS prescription swimming goggles. The first question is: ‘what’s my prescription?’

If you haven’t done so already, book an eye test with a professional optician to find out your prescription for standard spectacles. Use the formula below to work out the required dioptre and match each eye to the prescriptions offered for your chosen goggles.

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Your prescription should look like similar to this:

Swans Prescription Goggle Guide

The only numbers you need are the Sph (sphere) and Cyl (cylinder) values for each eye. Use the following formula to calculate the dioptre required:

Dioptre = Sph + (Cyl / 2)

Using the prescription example above:
Right eye = -2.0 + (-1.0 / 2) = -2.5
Left eye = -2.5 + (-2.0 / 2) = -3.5

If your dioptre falls between two of the options on offer, always move down to the next available dioptre. For example, if your prescription is -3.75 then move down to -3.5.

Does it matter if I have an astigmatism?

No. The above calculation will allow for your astigmatism and you will be ablse to see clearly in the water!However if your astigmatism is over 2.00 (as indicated by the cylinder value) - you may need to consider a custom made product.

Still confused?

We're here to help. Drop an email to, use our online chat at the bottom of the screen, or you can call us on 01202 606116.

It’s never been easier to get hold of SWANS prescription goggles, and they now come in a wide range of affordable styles and colours.

Take a look at our full range of prescription goggles here.