Frame Measurement & PD

We are often asked about frame measurements, P.D. (pupillary distance). Here follows some answers to the most common questions.

What is a PD?

A PD is one of a number of measurements to determine where to place the optical center of your prescription lenses into your frame. The PD tells us, horizontally, how to position the lens in front of your pupils.

While wearing the frame, we also take an OC (optical center) measurement which tells us the vertical position for the lens.

A PD measurement can be monocular (one per eye) or binocular (distance between eyes). A monocular measurement is most accurate as it captures any asymmetry based on how the frame sits on the bridge of your nose.

Will you measure my PD?

We are committed to patient choice; if the PD (or any other) measurement is available on your file from an exam or glasses purchase, we would be happy to provide you with a copy of that information.*

When is a measurement taken?

When you see us for an exam, an approximate P.D. measurement is taken during pre-testing for eye exams.

When we measure you for a glasses purchase, we use Optikam (see below) to take an accurate measurement of the glasses on your face.

What if I am not a customer?

We do not offer a standalone "PD measurement" service.  In that case, please contact the retailer where you are purchasing your glasses to have the measurement done.

* In British Columbia only, P.D. based on auto-refractor estimate is included on the spectacle prescription.  In other provinces it is available on request.

Optikam - the premium measurement tool

We use an advanced iPad-based device called the Optikam to digitally take 12+ position-of-wear measurements.  This includes P.D. as well as multiple additional measurements.

We know exactly how each frame fits on your face.

Measured in 0.1mm increments the Optikam is up to 5X more accurate than conventional measurement techniques.

Then we manufacture prescription lenses taking into account:

  • The doctor's prescription, and
  • How the frame fits on your face

Optikam measurements (compared to a manual measurement) are taken to improve optics, accuracy and comfort of the resulting prescription eyewear.

The Optikam process is exclusive to eyeglass lenses purchased in our clinic; we cannot measure the frame fit unless you are wearing the frame.

What measurements do we take?

From ONE picture, we obtain the following measurements:

  • Monocular Pupillary Distance (P.D.)
  • Multifocal Seg Heights
  • Optical center (O.C. height)
  • Pantiscopic Tilt (panto)
  • Vertex Distance (R.V.D.)
  • Wrap (face form tilt)
  • Near P.D.
  • A, B, E.D. and D.B.L. values (frame measurements)

Depending on the lens design, we are able to take in account some or all of these measurements to optimize your lens design and resulting visual acuity and comfort.

Why are accurate measurements important?

High quality vision requires premium ophthalmic lenses and precise measurement of those lenses to ensure they are placed correctly in front of your eyes.

Depending on the power of your prescription and lens design, a measurement error as small as 1mm can drastically change the power of the lens as well as how well your eyes work together.

Image deflection (called "prism"), image distortion and visual fatigue are common symptoms of poorly positioned lenses.

Your eyes are your window to the world - after investing in the time and cost of an eye exam, why compromise on the glasses you purchase? Trust an eye care professional (optometrist/optician) at Campus Vision to provide the best possible result with your prescription.