Glasses Prescription Explained

You've been to the optician, had your eyes tested and have the prescription in your hand. You are entitled to a copy of it once you've had your test and should be given a copy without having to ask nor should the optician imply that you have to buy your glasses from them.

To most people, a prescription is just a series of numbers. Understanding what the numbers mean can help you to input the information correctly, select your lens type and consider the most suitable options.

Entering the information is very easy and is simply a matter of copying the numbers from your prescription into the appropriate boxes.

You may find boxes on our website that you don’t have on your prescription available but simply ignore them.

Listed below is the different types of information and details you will find.

The basics of an eye prescription are a series of numbers for your right eye (R), and your left eye (L).

  • All numbers will be written in 0.25 increments
  • The unit of measurement for lenses is dioptres

You will sometimes see the Latin terms used for your eyes which are:

  • OS - (Oculus Sinister) for the left eye
  • OD - (Oculus Dextrus) for the right eye

Sometimes shorthand or abbreviations are used such as:

  • DV - (Distance Vision)
  • NV - (Near Vision) in place of the ‘ADD’

This image shows the various elements written on an eye prescription and what they mean:

Here is an example prescription:

Prescription glasses example

Here are the explanations of the different words and numbers:

SPH – (Sphere):

This box will have a ‘+’ or ‘– ‘symbol before the number.

This indicates if you are long sighted (+) and can see things far away, or short sighted (-) and can see things close up. The number refers to the power of the lens and the higher the number, the stronger the prescription lens is.

CYL – (Cylinder):

This refers to a condition called an ‘astigmatism’ and is caused by an irregular, or rugby ball shaped cornea. The higher the number, the more irregular the shape of your eye. This box may be blank on your prescription which means that you have perfectly round shaped eyes.


This number relates to the astigmatism and how much correction is needed in degrees to correct it and will be a number between 1 - 180.

Near or Inter ADD:

This number relates to prescriptions which require a reading or intermediate addition, hence the name ‘add’. As we age, typically around 45 years old, our eyes lose the ability to focus at a reading or intermediate distance. This number is the amount of correction required to see close up or in-between such as reading or viewing supermarket shelves or the dashboard of your car. If you have numbers in this box it means that you have a prescription for either or both: 'intermediate' or/& 'reading'. We recommend that you ask your optician when having your eyes tested to include 'Inter/Intermediate' lens power or information if it exists as they often will no do it unless asked or discussed in advance.

Pupil Distance:

Your pupil distance is exactly what it sounds like; it’s the measurement between your pupils.

This is often not written on your prescription but we recommend that you ask your optician to measure and write it down when having your eyes tested as they will likely not do it unless asked in advance. It’s important to know this measurement as it allows us to make your glasses with the lenses in the correct position.


This means that there is a muscle imbalance between your eyes and that they do not work well together as a pair. This prism correction will prevent double vision and correct the imbalance. Most prescriptions will not have this number.


This relates to the prism and the position of the lens and again, most prescriptions will not have this number.

Typical Styles/Layouts:

Glasses/lens prescriptions will have the same type of information on them but are written in a few different formats. This can sometimes cause confusion.

Here are some examples from different stores to show you the differences and how to decipher the information required:

Standard Format:

This is the format we have on our website and you simply copy the numbers exactly as they appear onto our lens ordering page:

 Prescription glasses example - standard format

Here are some examples of the different types and formats from the main high st providers:

Boots Prescription:

Boots prescription glasses example

Specsavers Prescription:

Specsavers prescription glasses example

Vision Express Prescription:

Vision Express prescription glasses example

Additional Information:

Your optician may add written notes or recommendations on the prescription for example suggestions of frame or lens type such as blue or anti-reflective coating, photochromic lenses and/or varifocal lenses. This is to give you the most comfortable vision correction possible for your needs.

You Must Be Given A Copy:

The General Optical Council (GOC) states that "an optician is obliged to provide you with the written prescription following the eye examination.

By law, the prescription must provide the basic results of the eye examination. You are then able to take the prescription to another supplier as you wish so that you can buy your glasses from a supplier of your choice.

Feel free to contact the optician if you require a copy of the glasses prescription at any stage.

Please don't hesitate to contact us should you require any further information and one of our advisers will be happy to assist you in selecting the correct lens options for your prescription, lifestyle and budget.

Freephone:0800 690 6220

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