Choosing the Right Prescription

Here we have given some advice on how to select the best prescription for your needs, but if you are in any doubt please contact us.


How do I choose the right power for me?

A spectacle prescription is usually written in the following form: sphere (or sph) / cylinder (or cyl) x axis

Usually the right eye is written first followed by the left, either one above the other or side by side:

R -3.00 / -0.50 x 180
L  -3.50 / -1.00 x 2


R -3.00 / -0.50 x 180 and then L -3.50 / -1.00 x 2

Occasionally right (R) and left (L) might be written as latin abbreviations OD (oculus dextrus) and OS (oculus sinister) respectively.

In order to calculate the power you need to take into account the two aspects of your prescription.

  • The sphere (or sph) is the main part of your prescription and will be ‘–’ for short-sightedness (myopia) and ‘+’ for long-sightedness (hypermetropia).
  • The cylinder (or cyl) is the secondary part of your prescription and refers to the amount of astigmatism you have.

You should base the power you order primarily on the amount of short or long sightedness you have. If you also have a moderate degree of astigmatism (up to 2.00), incorporate up to half of this to choose the most appropriate power. Most swimming goggles come in 0.50 steps so you may have to select the nearest power. You need to know the power and sign (+ve or -ve) of both parts of the prescription. Here are some examples:

  • -3.00/-1.00x90 - the best power would be -3.50 (-3.00 plus half of -1.00 so -3.00 plus -0.50)
  • -3.00/+1.00x90 - the best power would be -2.50 (-3.00 plus half of +1.00 so -3.00 plus +0.50)
  • +3.00/-1.00x90 - the best power would be +2.50 (+3.00 plus half of -1.00 so +3.00 plus -0.50)
  • +3.00/+1.00x90 - the best power would be +3.50 (+3.00 plus half of +1.00 so +3.00 plus +0.50

Unless you have a very basic prescription, most swimming goggles will not provide the same level of vision as your glasses or contact lenses. However, they will provide adequate vision for use in and around a swimming pool. If you are in doubt please contact us with your prescription and our optometrist can make a recommendation.


I have astigmatism, does that matter?  

Yes and no, it will depend on the degree of astigmatism. 

None of the 'off the shelf' goggles correct astigmatism so if the majority of your prescription is astigmatism, or you have astigmatism over 2.00 dioptres you will need a custom made product for best visual results.

If your astigmatism is less than 2.00 or is not the majority of correction then an 'off the shelf' goggle should be fine. See the question above on 'How do I choose the right power for me?' or contact us with your full spectacle prescription.


What is the highest prescription you can do?

In our 'off the shelf' goggles the highest we can do is -10.00 for short-sighted corrections and +8.00 for long-sighted corrections.

In our 'off the shelf' diving masks we can do -10.00 for short-sighted corrections and +4.50 for long-sighted corrections

In our custom made models we believe that we can make almost any prescription, simply contact us with your full spectacle prescription and we will be able to confirm availability and the cost.


How do I know your advice is correct?

We are owned and run by a qualified optometrist with over 25 years' experience who really understands your visual needs.

Our staff are trained to handle most queries themselves but are able to refer to the optometrist when they need more specialist knowledge.

Read more in our About Us section.


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