What are Progressives?
Progressives are no-line multifocal lenses with up to three viewing areas for near-, mid- and distance vision, so you can see up close and far away with one pair of glasses. As opposed to bifocals, which serve a similar purpose, progressive glasses are designed to correct at all distances without the visible dividing line.
What are Segment Height?
Segment Height (also referred to as Seg Height or SH), measures the distance from the bottom of the lens to the top of the bifocal line or the start of the progressive power of a multifocal lens. Seg height measurement only applies to bifocals or progressive lenses and not to single vision lenses. The seg height measurement for bifocal or multifocal lenses is specific to each pair of glasses, meaning that the bifocal segment height of your lenses may not be the same between pairs of glasses.
To measure your own segment height, all you need is:
- the frames,
- a ruler with millimeter measurements and
- a mirror (or a friend).
Because SH is specific to how the particular frame fits your face, you’ll need to wearing the frames when the measurement is taken. You can purchase the new frames without lenses first (click “Add Frame Only” on the product page) and then send them back to have lenses put in after the segment height has been measured.
How do I measure my own Segment Height?
Follow the instructions below to measure your own Segment Height at home.
- Download and print our Segment Height Ruler here, or use a ruler that has millimeter measurements.
- Put the glasses on your face and adjust them so that they sit comfortably.
- Stand about 8 inches (20 cm) away from a well lit mirror with your face parallel and square to the mirror.
- Align the ruler’s zero (0) measurement to the lowest point at the bottom of your lens, keeping it exactly vertical. Make sure you are measuring from the bottom of the clear lens, not the bottom of the frame
- Stare straight ahead, and read the millimeter line that lines with the center of your pupil. This is your segment height measurement for these frames.
- Repeat these steps at least 3 to 5 times to get an accurate and consistent measurement.
Measuring Tips
- Make sure your head and the ruler do not move after lining up the zero (0) measurement with the bottom of your lens until you note your measurement.
- Ask a friend to help if you are having trouble.
- If using a friend, keep your eyes as still as possible and look straight ahead.
- Look over their shoulder or above their head at something approximately 10-20 ft. away.
- Do not look at the person measuring!
In the absence of a ruler, your friend can simply use a fine tip permanent marker and make a small mark on the lens right at the center of your pupil.
There's an app for that!
While there are several apps that are out there to measure PD and Seg Height, the one that has been most recommended to us by our customers is the EyeMeasure App for iPhones and iPads. If you choose to try the app, please, as usual, take the measurement at least 3-5 times to get a consistent result. You can download it from the Apple App Store here. Please note, we have nothing to do with the development of the app, and we cannot guarantee its accuracy.