Do you have problems making sense of your Eyeglasses Prescription?

The numbers on your prescription relate to the corrected power of your vision and the shape of your eyes.

The numbers will help you to work out if you are shortsighted, longsighted or have astigmatism.

You would usually see the chart written with R (right Eye) and L (left eye)

You will see SPH (sphere), CYL (cylinder), Axis (X), followed by Add (reading magnification) Int ADD (intermediate magnification usually for computer distance) and HPrism (horizontal Prism) or VPrism (vertical prism).

But what does this mean?

Sphere (SPH)

Sphere power is measured in diopters (D) and indicates the amount of lens power prescribed to correct short or long sight.  

The number is usually prefixed with a plus (+) or minus (-)

If the number under this heading has a plus sign (+), you are longsighted.

If the number under this heading comes with a minus sign (–), you are shortsighted.


Cylinder (CYL)

Cylinder indicates the amount of lens power needed for astigmatism (visual distortion) which is caused by an irregular shaped cornea (oval shape). If this box is empty, there is no astigmatism, and your eyes are perfectly spherical.

The higher the number, the more oval shaped your eyes are.


Axis (X)

If an eyeglass prescription includes cylinder power, it also needs to include an axis value, which follows the cylinder power and is often written as ‘X’

The direction of astigmatism is measured in degrees between 1 and 180.  The lab will use this information to position your lenses.



‘Add’ is the added magnifying power applied to the bottom part of multifocal or bifocal lenses to correct presbyopia (ageing eyes).

It happens to us all with age!

Presbyopia is a condition in which the lens of the eye loses its ability to focus, making it difficult to see objects up close.

You start to stretch your arms out to see but eventually you must join the over 40’s gang and buy glasses. No one can escape presbyopia even if you have never had a vision problem before.

The number is usually dependent on age and appears as a plus (+) power between +0.75 to +3.00 and is often equal in both eyes.

You may see

ADD (near vision correction)

Int. ADD (intermediate vision correction often used for computer distance)



Only a small percentage of eyeglass prescriptions include a prism measurement.

Prism usually means your eyes have had a bit of a fall out and aren’t working together as a pair. This often causes double vision and headaches, just like when you fall out with your other half 😍

The power is indicated in decimal form (can also be written in fraction form) with a direction indicated.

The base simply lets the lab know where to place the prism in your glasses.

HPrism (Horizontal Prism)

BI = Base in (towards your nose)

BO= Base out (towards your ear)


VPrism (Vertical Prism)

BU= Base up

BD= Base down

Feel free to hop on the phone for a chat, happy to talk you through your script.

Call 08 6117 2661


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