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Prescriptions (Rx)

What does my prescription (Rx) mean?

Your Rx is what an ophthalmologist (an MD) or optometrist (a doctor of optometry) provides to correct your vision with a pair of eyeglasses with corrective lenses.

Can I get a list of optical abbreviations?
Here is a list of some optical abbreviations that will help you order your glasses from WhereLight:

ADD(also NV-ADD):The Near Vision (NV) Reading ADDition correction on a multifocal Rx. Can be used for bifocal or progressive glasses, or for single-vision reading or computer (intermediate) vision glasses.

AR:Anti-Reflective. A coating that reduces reflection on the lenses.

AXIS:The angle at which the Cylinder (CYL) is placed on a lens to correct an astigmatism. It ranges from 1 to 180.

BAL:The Rx calls for balance lenses, meaning the same Rx for each eye. Often used when a person has no sight in one eye, so both lenses will have the same thickness.

BD, BI, BO, BU:A prism correction on your Rx (may be indicated with Δ, and one of these four abbreviations. The B stands for base, and it could be base down (BD), base in (BI), base out (BO), or base up (BU).

CYL:The Cylinder. Combined with the , the CYL corrects an astigmatism.

DS:The abbreviation for . An eye dr. may write DS on an Rx in the field if no astigmatism correction is needed.

DV:Distance vision.

FT:Flat-top bifocal.

NV:Near vision.

NV-ADD (also ADD):The Near Vision (NV) Reading ADDition correction on a multifocal Rx. Can be used for bifocal or progressive glasses, or for single-vision reading or computer (intermediate) vision glasses.

OD:Latin for Oculus Dexter, meaning the right eye.

OS:Latin for Oculus Sinister, meaning the left eye.

OU:Latin for Oculus Uterque, meaning each eye.

PAL:Progressive Addition (or Adjustment) Lens: sometimes on a Progressive Rx an eye dr. will write two different numbers for the NV-ADD, perhaps +2.25 and +2.50, to increase the reading power in the NV-ADD for Progressive lenses.

PD (Pupillary Distance):The PD is the measurement of the distance between your pupils. This is needed for the manufacturer of the eyeglasses to know where to place the optical center on each lens, so you can see well with the glasses.

PL:Plano. Latin for ""flat."" If this is in the SPH section of an Rx, it means no nearsighted or farsighted correction is needed.

RX:A prescription.

SPH:The first section on an Rx. It corrects nearsighted or farsighted vision.

UV:The abbreviation of ultraviolet. UV light is invisible to the human eye, but it is UV light that gives us a sunburn, and too much exposure to it can damage the eye. All of the lenses WhereLight offers come with 100 percent UV protection, for free.

VA:Visual acuity: how well the eye can see. Sometimes this may be written on an Rx, with a number such as 20/20. This would indicate that with eyeglasses made to this , the vision would be corrected to 20/20 vision.

What is my pupillary distance (PD) and how do I get it?
○ What's Pupillary Distance?
Pupillary distance (PD) is the distance measured in millimeters between the centers of the pupils of the eyes. This measurement is different from person to person and also depends on whether they are looking at near objects or far away.
○ Printable PD Ruler

Print this page on A4 without scaling, at 100%.

Fold the ruler along the dotted line.

Mirror or Friend
Position yourself arm's length from your friend or yourself approximately 8 inches (20cm) away from a mirror.
Download Wherelight's PD ruler
○ How to measure your PD?
Close your left eye and align the 0mm over the center of your right pupil. Place ruler against forehead for stability.
Next, open your right eye and close your left eye.
Note the reading directly over your left pupil. That will be your PD. (Most adults have a PD that falls between 57 - 72mm)
Can you fill strong prescriptions?
Single-vision Rx:

Up to -20.00 or +12.00 on the Sphere (SPH)

Up to + or - 6.00 on the Cylinder (CYL).

Bifocal Rx:

Up to -9.00 or +6.00 on the SPH.

Up to + or - 6.00 on the CYL.

Up to +3.50 on the NV-ADD.

Progressive Rx:

Up to -10.00 or +8.00 on the SPH.

Up to + or - 6.00 on the CYL.

Up to +3.50 on the NV-ADD.

Prism (single-vision only):

Up to 5.00 in any direction.

What if I have an astigmatism?
Most people have an astigmatism. If you have an astigmatism on your Rx, we can make glasses that will correct it.
Do you offer bifocal or progressive lenses?

Yes! We offer both. If you have ADD or NV-ADD on your Rx, you can get lined bifocals or unlined progressive glasses.

How do I order reading glasses?

If you have a glasses prescription with an NV-ADD, it is best to order Prescription Reading Glasses. If you do not have a glasses prescription and typically buy reading glasses from the drugstore, you may consider Over the Counter Reading Glasses.

Prescription Reading Glasses

It is easy to reconfigure an Rx with an NV-ADD. It just involves a little grade-school arithmetic.

You simply take the NV-ADD number on your Rx and add it to the numbers in your Sphere (SPH) category for each eye. Then lower your distance PD by 3 millimeters if it's the single PD, by 1.5 millimeters for each eye if it's the dual PD. That gives you an Rx for single-vision reading glasses!

How to convert prescription into reading glasses prescription

If you are used to buying reading glasses over the counter from the drugstore, you can easily buy them from WhereLight as well – with even more benefits.

Start by picking your favorite frame. Once you know your recommended reading power (such as +2.00), select “Single Vision” as the Prescription Type, and enter the same power for each eye in the Sphere (SPH) category. Do not enter a value in the CYL, Axis, or Prism boxes. You’ll need to lower your distance Single PD by 3 millimeters.

Can you fill prescriptions with prism corrections?

Yes we can.

Can I use my contact lens prescription to order glasses?

Sorry, a contact lens Rx can only be used for contact lenses.

How do I order non-prescription glasses?

It's super easy to order glasses from WhereLight! After clicking on the Order Glasses button, select Non Prescription at the Prescription Type drop-down window. During the ordering process, you can also choose our Beyond UV Blue Blocker lenses and/or add anti-reflective coatings.

What if my prescription has expired?

We strongly recommended that you get an eye exam every two years, or more frequently if you notice that your vision has changed.

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