pd information

Find your measurement

There are some important measurements and information that we need to process your lenses correctly before ordering.

Eyeglass Prescription

Segment Height (SH)
Pupillary Distance (PD)
Ocular Center (OC)
Your eyeglass prescription

There are a few ways you can provide us your prescription:

  1. Enter your prescription online before you place your order.
  2. Email a copy to us at info@todaysoptician.com
  3. Upload a photo.
  4. Send a copy later with your frame.

The prescription must be less than 2 years old, unless otherwise stated with an expiration date.

Please note: We can also duplicate the lenses in your current frame if you do not have a valid prescription.

Understanding your eyeglass prescription

Need Help Understanding Your Prescription?

OD: Stands for “oculus dextrus”, Latin for your right eye.

OS: Stands for “oculus sinister”, Latin for your left eye.

Sphere (SPH): This is the lens power, prescribed to correct for nearsightedness or farsightedness.

  • If the number has a minus sign (–), you are nearsighted.
  • If the number has a plus (+), you are farsighted.

Cylinder (CYL): This is the lens power for astigmatism. If nothing appears in this column, either you have no astigmatism, or your astigmatism is so slight that it is not necessary to correct it.

  • If the number has a minus sign (–), you have a nearsighted astigmatism.
  • If the number has a plus sign (+), you have a farsighted astigmatism.

Cylinder power is always after sphere power in an eyeglass prescription.

Axis: The axis defines the location of the cylinder powers on the lens with a number range from 1 to 180. Axis is only listed if you have a Cylinder correction on your Rx.

PD: Stands for “pupillary distance”, the distance between your pupils.

What is Single vs Dual PD?

SINGLE PD is the pupillary distance between the center of one pupil to the other, which can be a distance PD or near PD. Distance PD is used to order any type of prescription glasses except for reading glasses.

DUAL PD, or monocular PD, consists of two numbers and is the distance between the centers of each pupil to the center of the nose. Dual PD is usually written in the following way: 33/31 (right eye, left eye).

ADD: This value  is usually used for bifocal or progressive lenses, as well as for reading glasses. Your doctor may write your ADD in the near vision (N.V.) or ADD section.

Prism Correction: This correction is for those who either have exotropia or esotropia.  It is written as Base down, up, in or out.  There is no additional charge for prism below 4 D.  Please notify us if you have any questions.

 

Prescription example:

 

Entering your Rx on todaysoptician.com:

 

Measuring your pupillary distance (PD)

PD indicates the measurement in mm of the distance between the centers of your pupils.  It is a necessary measurement that ensures your new lenses are manufactured accurately.

Occasionally the PD is written on your prescription from the doctor.  If you don’t have your PD, we can measure it for you in just a few simple steps.

Measure PD yourself

There are several options that you can use to provide us your PD measurement.

1. Upload a photo

YOU WILL NEED: a camera, or cell phone, and a standard wallet-size card (ID, Drivers License, member card, Credit Card, etc).

  • Remove your glasses.
  • Press the card horizontally under your nose.
  • Snap a selfie!
  • Send us the image on the checkout page.
  • We will then take your photo and measure your PD for you.

View Steps

View Example Image

2. Download our PD ruler

YOU WILL NEED:  a mm ruler, and a mirror.  Or have a friend help you.

  • Stand 8-10 inches in front of the mirror with the ruler level just below your eyes.
  • Close your left eye, and align the “0” on the center of your pupil.
  • Continue looking straight, now close your right eye and open your left eye.
  • Read the number value on the center of your pupil of your left eye.
  • Record this measurement and enter it on the checkout page.

Download our PD ruler

What is Single vs Dual PD?

SINGLE PD is the distance between the center of one pupil to the other, which can be a distance PD or near PD.  Distance PD can be used to order any type of prescription glasses except reading glasses.

DUAL PD, or monocular PD, consists of two numbers and is the distance between the centers of each pupil to the bridge of the nose.  Dual PD is usually written in the following notation: 33/31 (right eye, left eye).

Measuring your Ocular Center (OC), Seg Height (SH)

Ocular center, or optical center (OC), is the vertical measurement in mm from the bottom of the lens in your frame, to the center of your pupil.

Segment height, or seg height, is the vertical measurement in mm from the bottom of the lens in your frame, to the center of the progressive lens, computer lens or the top line of the segment on a bifocal.

At Today’s Optician, and most online glasses and lens retailers, these measurements are crucial to processing your lenses accurately.

How to measure your SH, and OC

There are several options that you can utilize to provide us the SH and OC measurement.

1. Upload a photo

YOU WILL NEED: a camera, or cell phone, a standard wallet-size card (ID, Drivers License, member card, Credit Card, etc), and the frames you need the measurements for.

  • Keep your glasses on.
  • Press the card horizontally under your nose.
  • Snap a selfie!
  • Send us the image on the checkout page
  • We will then take your photo and measure your OC and SH for you.

View Steps

View Example Image

2. Download our PD ruler

YOU WILL NEED: a mm ruler, and a mirror. Have a friend help you.

  • Use the downloaded mm ruler folded in half, and position the “0” value at the bottom of the lens, not the frame.
  • Read the value at the center of your pupil. This will be the OC (Single vision), or the SH measurement (Computer, Progressive).
  • For Bifocals, read the value at the mid part of the lower lid. This will be the Bifocal SH measurement.
  • Record this measurement and enter it on the checkout page.

Download PD Ruler

How to videos…

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