How to Take Measurements for Prescription Eyeglasses Online

Taking measurements for prescription eyeglasses is a skill that requires training and practice. Most opticians train for at least two years to learn optical dispensing, which includes measuring for eyeglasses and understanding different specific requirements for a variety of lenses and vision problems. Although you can take your own prescription eyeglass measurements, it is much better for another person to do the measuring. Ordering eyeglasses online is fairly easy, but there are specific things to keep in mind when taking measurements for prescription lenses.

Things You'll Need

• Ruler with millimeters
• Dry erase marker

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Instructions

Measure the PD

• 1

  Measure the PD, or pupillary distance. This is necessary for every pair of prescription lenses. The PD is a measurement in millimeters of the distance between the pupils. There are two types of PD: monocular which is the distance from each eye to the center of the bridge or nose and binocular, the distance from pupil to pupil.

• 2

  Place the ruler with millimeter markings so that the zero line is centered in the middle of the right pupil. Hold the ruler horizontally and measure across to the center of the left pupil.

• 3

  Note the number. Most optical laboratories use binocular PD. An average measurement for a binocular PD will be between 58mm and 70mm. A monocular PD will average 29 to 35mm. Monocular PD is used for high-power or complicated prescriptions and progressive bifocals.

Measure for Bifocals

• 4

  Place the frame on the person you are measuring. If you are measuring yourself, sit so you are able to look straight ahead into a mirror.

• 5

  Draw a line with a dry erase marker on the plastic lens of the eyeglasses along the edge of the lower lid, near the lashes, for both eyes to measure for bifocals.

• 6

  Remove the glasses and measure from the deepest part of the bottom of the frame to the line. This measurement is called the bifocal height. To measure for trifocals or progressive lenses, also called no-line bifocals, draw the line at the bottom of each pupil.