How To Read Your Glasses Prescription
When you visit the opticians for an eye test you will receive a written copy of your prescription. At first glance, the details may seem quite confusing. You've probably asked yourself many times, what does my glasses prescription mean? But don't worry, after reading this page you'll understand what all the details mean and you'll know how to read your glasses prescription correctly.
How To Read Your Glasses Prescription Correctly
On this page, you will discover:-
- The layout of your glasses prescription.
- What the values on your prescription mean.
- Different ways a prescription can be displayed.Common abbreviations that appear on your prescription.
- How to enter your glasses prescription online.
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.
What The Values On Your Prescription Mean.
When reading your glasses prescription you will find values under the headings of SPH, CYL, AXIS and sometimes PRISM & BASE
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 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.
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 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 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).
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).
Different Ways A Prescription Can Be Displayed
A glasses prescription can be displayed in a number of ways. The images below show the same prescription information in two different formats.
As you can see in the first example (Standard GOS 2 Glasses Prescription) the optician has listed the patient's complete distance prescription on the top row and the complete near prescription in the bottom row.
The second prescription 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.
Common Abbreviations That May Appear On Your Glasses Prescription
OD - Right eye
OS - Left Eye
Balance - No values are required. This instructs the person making your glasses to use a lens of similar weight to balance out the frame.
Plano, Infinity, 0.00, - Basically 0.00 or no correction is required for that part of the prescription.
Add, Near Add, Reading Addition - These all relate to your reading addition and can be written anywhere on the prescription.
Inter, Inter Add, Int Add, Int, Intermediate Addition - These all relate to your intermediate addition and are used to make glasses for intermediate distance use. They can also be written anywhere on the prescription.
VA, Visual Acuities - These values describe your vision (visual acuity) but are not needed to make your glasses.
BVD - Back Vertex Distance is the distance required from the front of your eye (cornea) to the back surface of the corrective lens. If you have been provided with a BVD value ensure to enter it into the additional information or comments box provided with any online prescription forms.
How To Enter Your Glasses Prescription Online
Do not worry about entering your prescription details online. Most reputable online suppliers like Spex4Less will offer a variety of forms for you to enter your prescription details in to.
Our online prescription form initially displays the most common format, Distance with a Near Add. However, underneath the form, you will see a set of links under the heading "Click here of your prescription looks different to this form". These links allow you to toggle the form so that it appears the same as the hard copy of your prescription (see image below). You can simply select the values that match your prescription. This is especially handy as you can copy the values without having to make any calculations yourself.
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. Here at Spex4Less, you will find both of these options directly above the prescription form.