How do you read an optical prescription?

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1. The layout of your glasses prescription.

Naturally, a prescription will contain values for the correction of both of your eyes. The values concerning the correction your right eye may be indicated as "RE", "Right", "Right Eye" or "OD" which is an abbreviation for Oculus Dexter, the Latin term for "Right Eye".

Similarly, the values concerning the correction of your left eye may be indicated as "LE", "Left", "Left Eye" or "OS" which is an abbreviation for Oculus Sinister, the Latin term for "Left Eye".

You should also find a row of values provided for "Distance" and for "Near". Alternatively, you may have a row for "Distance" and a space provided for a "Near Addition" or "Reading Addition".

The "Distance" row contains the values required to correct your distance vision for the respective eye. The "Near" row or "Near Addition" contains the information required to correct your near vision.

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2. What the terms on your prescription means.

When reading your glasses prescription you will find values under the headings of SPH, CYL, AXIS and sometimes PRISM & BASE

SPH (Sphere)
SPH is a + or - value in 0.25 steps and is required to correct your nearsightedness (-) or farsightedness (+). In some cases the optician may write what appears to be a slash above the figure to indicate a "-" value.
When no correction for SPH is required the optician will write "Plano", "∞", "0.00" or just leave the space blank.

CYL (Cylinder)
CYL is a + or - value in 0.25 steps and is required to correct your astigmatism. If you have an astigmatism, you will find a "+" or "-" value in this box. You will also have a corresponding "AXIS" value (see below).
When no astigmatism correction is required the optician will leave the box blank. They may also enter an abbreviation "DS" (Dioptre Spheres) or "SPH" (Sphere) indicating that the correction required is spherical only.

AXIS
An AXIS will only be found on your prescription if there is a CYL value for the same eye. The AXIS, in degrees, is a number between 0 and 180. It is used to correctly orientate the cylinder correction when making your glasses. On some rare occasions, you may find an AXIS value with a decimal place or fraction.

PRISM
Prism is used to correct eye alignment issues and can be a metric or fraction value. For example, "1.5" or 1½. The PRISM value will also be followed by a directional value (see BASE below). Only a small amount of prescriptions will require a PRISM.

BASE
Base is the direction of a PRISM value and will only be supplied if the prescription has a PRISM value. The BASE value will be displayed as BU or UP (Base UP), BD or DOWN (Base DOWN), BI or IN (Base IN) or BO or OUT (Base OUT).

ADD
The ADD value is also referred to as a "Near Addition" or "Reading Addition". This is always "+" value in 0.25 steps. It is the amount of magnification required to "ADD" to the "SPH" value of your "Distance" prescription to correct your near vision.

The "ADD" value may be written in the "Near Addition" space on your prescription. However, many opticians will simply write the value somewhere under, or next to, the distance values. For example: "+2.25 ADD" or "Add +2.25". The "ADD" value applies to both eyes and can sometimes be written only once on the prescription, even though the addition is required for both eyes.

There are occasions where your optician will write out your complete "Distance" prescription followed by your complete "Near" prescription. If this is the case, your prescription will display SPH, CYL & AXIS values in both the "Distance" and "Near" sections of the prescription. (See Different ways in which a prescription can be displayed below).

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3. Different ways a prescription can be written.

A glasses prescription is usually displayed in two different formats:

Standard GOS 2 Glasses Prescription Form

Distance & Reading Add Glasses Prescription

For the Standard GOS 2 Glasses Prescription the optician has listed the patients complete distance prescription on the top row and the complete near prescription in the bottom row.

The second prescription (Distance & Reading) shows the patients complete distance prescription for the right and left eye followed by a reading addition value of +2.25. This value is the amount to add on to the distance SPH values to ascertain what the full Near prescription should be. For example: (+2.00) + (+2.25) = (+4.25). You'll notice the CYL and AXIS values are the same for both distance and near.

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4. Typical Abbreviations used on prescriptions.

5. How to enter your prescription online.

Most reputable online suppliers like Shade Files will offer an easy-to-use prescription input form like the here.

Our online prescription form allows you to take the information from your script and input using simple drop-down selectors.

If you are still unsure about entering your prescription details when ordering glasses online, make sure that you choose a supplier that offers an "Upload" or "Send Later" option. Shade Files provides both of these options at the start.