How to read your eyeglass prescription
Learning what all those signs and symbols mean is crucial for you to take control of your eye health.
So, let’s start with a very brief explanation of what the abbreviations on your prescription actually mean:
overdose it is dexterous oculus which means that you Right eye
BONE it is sinister oculus which means that you left eye
HPS it is sphere – the main part of your recipe. Indicates the strength of your prescription in diopters.
CYL it is cylinder – indicating the strength of your astigmatism (if any).
AXIS is the rotation of the cylindrical lens (CYL) that runs in a plane from 1-180 degrees.
IT IS it is flat – meaning no vision correction is needed (basically you want frames equipped with clear glass lenses for fashion purposes).
YOU medium distance vision
Snowfall medium close up vision – sometimes says NVO
ADD is short for additional value
database is the distance between your pupils or pupil-distance
WHERE it just means both eyes
COMRADE stands for additive progressive lens and is the added value for your progressive lenses.
Balance it means that one eye has a prescription and the other eye has no useful vision.
X is short for Axis.
Prism It happens when both eyes are not properly aligned and need a prism to realign them.
Base is the rotation of the prism. The recipe will say:
BO – base off
BI – based on
Drank – bottom up
comic books – base down
Every doctor writes their prescription differently, so one really needs to take note of the abbreviations and calculate the meaning accordingly.
Note: numeric values will always be written with a plus (+) or minus (-) sign in the SPH, as well as in the CYL and ADD. These signs are probably the most crucial of the entire prescription, as mixing them together will determine how and if you can see.
As stated above, SPHERE (SPH) is the potency of your recipe in 0.25 increments. People who are nearsighted (distant vision) will generally have a minus sign (-) on their dial, while people who are farsighted (difficulty seeing up close) will have a plus sign (+) on their prescriptions.
Your optometrist or eye doctor may also have written your SPH or CYL as +150, which is equal to +1.50.
For those with ASTIGMATISM, you will have a note on your prescription for your CYLINDER (CYL). Basically, this is when your eye is curved and that curvature makes your vision blurry unless corrected. Some people may only have astigmatism in one eye and many people may not have astigmatism at all, in which case that field will be left blank. Alternatively, they will write SPH, 00, Plano, or DS, which means you have no astigmatism.
If you have a CYL, you will also have an AXIS, which tells you what grade that CYL lens should be made to. The axis must be between 1 and 180 degrees and will always be an integer. If your axis is written as “6”, it can be entered as 06 or 006.
The ADDITIONAL VALUE (ADD) is most commonly used for multifocal glasses as well as single vision reading glasses. You should look carefully for these numbers, as your doctor may write them in the near vision (NV) or ADD sections, or simply indicate on the side that it is ADD. There are times when your doctor will only write the ADD once, meaning it’s for both eyes, while other times (and more correctly), each eye will be given its own value. Distance single vision glasses do not require an ADD reading and this can only be omitted from your order form, although it is recommended for best vision. Those who need special glasses such as reading glasses, progressives or bifocals, MUST include this information to avoid manufacturing errors.
Your pupillary distance (PD) isn’t usually written on your prescription, so you should always check it before you leave your doctor’s office. The average PD is 62mm and most people fall within the range of 54mm to 74mm. Measuring your own PD is complicated and needs to be done by a professional. It is never wise to guess this, otherwise the optical center of the glasses will not align with your pupils, giving you headaches and not being comfortable.
Your PD can be written in different ways, ie: 63; 32/32; 33/31; 30.5/33.5; 63/60.
If your PD is written as 63, just enter it as 63. If your PD is written as 32/32, you can add the two and enter 64, or you can write each number separately. If your PD is written as 33/31 or 30.5/33.5, the measurements from the center of the nose to the pupil in either eye are not the same and you must enter your PD as written on your prescription. Do not do add the numbers.
Remember, with all that said and done, the most reputable online eyewear companies will also allow you to email or fax your prescription to them so they can double check that everything is correct OR so they can just fill it out for you.