Understanding Glasses Prescription: How to Read It

Understanding Glasses Prescriptions in IE: A Comprehensive Guide

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After an eye examination, your optician is lawfully required to give you a copy of your prescription. This is an order that uses a mixture of numbers and letters to specify what correction you need. Once you have got your prescription, you can easily get your choice of glasses. If you’re unsure, you can consult your optician and ask for their advice about the material of the frame you should go for. For instance, those with high power are advised to go for plastic/acetate frames as the acetate material conceals the thickness of the lens.

Understanding a glasses prescription can be tricky, especially for those who haven’t seen one before. So, if you’re wondering how to read a glasses prescription, we’ve broken down the different parts of your prescription to make it easier for you to understand.

What do the symbols on my prescription mean?

On your glasses prescription, you’ll find symbols and terms such as (+) and (CYL). In order to read your prescription, you’ll need to get familiar with what these symbols and terms mean.

+ or - Sphere (SPH)

On your prescription, you will see a ‘+’ or ‘–’ sign followed by a number. This is the SPHERE (SPH) value.

'+' means you are long-sighted, meaning you are unable to see close-up objects clearly.

'-' means you are short-sighted, meaning distant objects appear blurred.

Sometimes, you may find the ‘+’ or ‘-’ sign is written above the number. The sphere value is measured in dioptres (D), going up in steps of 0.25.

If you see Plano, PL Infinity (∞) or 0.00 mentioned on your prescription, this equals zero, and means there is no spherical correction.

ADD

ADD is the additional correction required for reading; therefore, won’t be on every prescription. It is also written as near addition, near add or NV. This value is added to the sphere to calculate your near vision prescription.

An ADD can range from +0.25 to +4.00 (it goes up in steps of 0.25).

You may also come across Intermediate ADD (IV) on your prescription. This is for those who struggle to see at arm’s length distance, i.e., when using a computer screen.

Cylinder (CYL)

You’ll also see a cylinder (CYL) number on your prescription, usually in a ‘+’ or ‘–’ format. This refers to the level of astigmatism and it can start as small as +/-0.25 for spectacle prescriptions.

An empty box or DS means there is no astigmatism.

OS and OD

OD refers to the right eye. OS refers to the left eye.

In some cases, you may come across ‘OU’ or ‘ODS’. This refers to both eyes.

AXIS

The axis number on a prescription indicates which direction they should position the CYL or cylinder. This is required for people with astigmatism. This can range between 1 and 180 degrees for spectacle prescriptions.

Prism

This shows if you have a muscle imbalance in your eye and is prescribed to prevent headaches or double vision.

The amount of prism is recorded in dioptres and can be written in decimal form or sometimes as a fraction and will always have a direction, for example, 1.50D Base UP.

PD (pupillary distance)

Measures the distance between your eyes, from the centre point of one pupil to the other.

In most cases your optician will not add this to your prescription.

Other symbols

You may come across other symbols on your prescription, such as BAL (balance), VA (visual activity), and BVD (back vertex distance).

VA and BVD are not required to place your order online.

Different types of glasses prescriptions

Prescriptions vary per individual. However, there are also different variations of prescriptions.

Single-vision prescription

Single-vision lenses are used in glasses to correct short-sightedness (myopia), farsightedness (hyperopia), and presbyopia, which is a gradual loss of the eye’s ability to focus close up. They use just one prescription and can be used for everyday use, such as reading and driving.

Lined bifocal prescription

Lined bifocal lenses contain two prescriptions. One is for near vision and the other is for distance. The top half of the prescription is usually for distance and the bottom half of the prescription is usually for near vision. Traditional lined bifocal lenses have a clear, visible line to separate prescriptions.

Bifocal prescriptions can be identified on a glasses prescription by numbers in the ADD column.

Progressive or multifocal prescription

Progressive lenses contain three prescriptions: one for distance vision, one for intermediate vision and one for closeup vision. Progressive lenses allow you to experience all three visions without a visible line of separation and are ideal for people who need to use a computer.

This can also be identified on a glasses prescription by the numbers in the ADD column.

How to apply your glasses prescription

A part of understanding your prescription is learning how to enter it when ordering your glasses. Here are some examples of prescriptions provided by opticians and how values should be entered when ordering glasses from Feel Good Contacts.

Specsavers

Vision Express

Vision

Boots

NHS

The ADD value will not always be mentioned (or necessary if you’re entering a prescription for distance). In this case, just leave it blank.

Why is my pupillary distance not on my prescription?

Your pupillary distance, also known as PD, is the measurement between the centre of your pupils. It indicates which part of the lens in your glasses you look through.

If you can’t find your pupillary distance on your glasses prescription and think your optician may have made a mistake, rest assured, this information isn’t included on your prescription.

However, you will need this information when ordering your glasses as it is used to ensure your vision is comfortable and clear.

Sometimes your optician will provide you with this information after an examination, however, if they don’t, you can simply measure it yourself using these steps:

Stand in front of the mirror
Look straight ahead and place the ruler on the bridge of your nose
With one hand, make sure that the ruler starts on your right pupil
Measure the distance between your right pupil and your left pupil
The number will be your pupillary distance

A glasses prescription may look daunting after your first eye examination, but remember, as long as you understand the symbols and terms, you’ll be able to apply them to your glasses, no matter where you’ve had your eyes examined.

For all your eye care needs, including glasses, sunglasses and contact lenses, shop with Feel Good Contacts.

If you have any questions regarding your glasses prescription, get in touch with our lovely customer service team, who will be more than happy to help you.