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Understanding your spectacle lens prescription

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Understanding your prescription can be a little confusing, with so many abbreviations and numbers, it’s easy to forget what it all means. Here's a quick overview to refresh your memory.

Whether it’s your first time being prescribed spectacle lenses to correct your vision, or you’ve been wearing spectacles for years, understanding your prescription can be a little confusing. With so many abbreviations and numbers, it’s easy to forget what it all means!

It’s important to have regular eye examinations; it is recommended to see an optician every 2 years, unless you have been advised otherwise by your optician. Eye examinations can ensure you are wearing the right spectacle lenses for your vision needs and can also uncover any other health issues such as cataracts and glaucoma. With that being said, it’s key that you leave your opticians understanding the condition of your vision and what that means.

Eye examinations can help identify health problems

Your prescription is often displayed in some form of table, with various abbreviations, words and numbers to describe the outcome of your eye examination. So, if you need a helping hand in deciphering its meaning, look no further.

What does your spectacle lens prescription mean?

You will most likely see a number of different abbreviations along the top. SPH (sphere) refers to the amount of lens power, which is measured in dioptres (D). If you see a ‘+’ sign in front of the number, this indicates that you are long or far-sighted, which means you find it difficult to see things close up. If you see a ‘-‘ sign, you are short or near-sighted, which means it’s difficult to see things far away. The higher the number that appears after the plus or minus sign, the stronger the prescription lens required to correct your vision.

CYL (cylinder) will indicate if you have astigmatism, something that is caused by an irregularly shaped cornea. Astigmatism is a common defect that occurs when the curvature of the cornea or lens is not uniform, and is usually present from birth. 
If there is nothing written here, then you either don’t have astigmatism, or it is so minor that it isn’t necessary to correct with lenses. If you see a low number, for example 0.25, then your eyes are only slightly irregularly shaped. A higher number such as 3.00 can indicate that your eyes are quite oval in shape.

AXIS denotes the direction of your astigmatism, measured in degrees. It measures the orientation of the cylinder from 0-180 degrees, and lets the lab know how to position your lenses correctly. 

PRISM refers to any correction that is needed to align your eyes. A number in this box usually indicates that your eyes need spectacle lenses to help them work as a pair. Prismatic lenses will correct this by bending the path of light without altering focus. 

BASE is related to your prism prescription, and will specify which direction the prism needs to redirect the light in.

If you are over 40, you might see ADD at the bottom of your prescription. This is the reading addition to your prescription if you have presbyopia. The number in this box will refer to the amount of additional correction required for seeing objects at closer distances. Generally speaking, the ADD measurement will be the same for both eyes and will range from +0.75 to +3.50.

You might also see ‘OD’ and ‘OS’ written to the side of your prescription. These are simply abbreviations for ‘oculus dexter’ which is Latin for right eye, and ‘oculus sinister’ which is Latin for left eye.

Prescription lenses for your favourite glasses

Take control of your vision with Essilor

If your next eye examination is due, why not ask about Essilor lenses? With lens solutions and enhancements for every vision need, we are the #1 spectacle lenses manufacturer worldwide(1)


1)     Euromonitor Eyezen 2019 edition, Essilor International SA Company. Retail value sales at RSP.

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