How to Measure Progressive Lenses

Progressive lenses are no-line bifocals that allow you to see at multiple focal points, including long distance, intermediate and in between. They are called "progressive" because the power gradually changes through progression from distance in the top, through an intermediate range in the middle and to near vision in the bottom portion of the lens. Care must be taken when measuring the placement of the progressive lens in a frame.

Things You'll Need

• Ruler with millimeter marks

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Instructions

• 1

  Place the frame on the person to be measured. Ensure that the frame sits snugly and as close to the face as possible. Make sure the eyes are centered and located in the top half to top third of the lens. The best fit for progressive lenses is to have a slight tilt to the lenses, with the top of the frame set slightly farther away from the forehead and the bottom of the frame set slightly closer to the cheeks.

• 2

  Place the ruler vertically in front of the person's right eye. Line up the zero line of the millimeter to the bottom edge of the person's right pupil.

• 3

  Measure down the ruler to the inside edge of the bottom of the rim. Instruct the person to look straight ahead as you measure. Double check the measurement and note the number. Repeat the process for the left eye.

• 4

  Determine that the frame is a good candidate for the progressive lens. Lens manufacturers have specific guidelines for fitting their lenses but a good rule of thumb is to make sure the no-line measurement is at least 20 millimeters. Some progressive lenses can be as short as 15 millimeters. The deeper the lens, the better the progressive lenses will work.

• 5

  Measure the pupillary distance, also called PD. This is also measured in millimeters and is important for centering the progressive lens. Instruct the person to look straight ahead and measure the distance between the center of the right pupil and the center of the left pupil. Note the number.

• 6

  Measure the reading PD. Instruct the person to look at the tip of your nose. Measure the distance between the center of the right and left pupil. This number is usually approximately 3 millimeters less than the distance PD.