If you know your U.S. history, there have been several attempts to adopt the metric system, all to no avail. It's the universal standard for most of the world and way more intuitive, yet the chances ...

The pupillary distance (PD) measurement is a requirement for people who want to purchase eyeglasses. Here, find out how to measure your PD using a mirror and a ruler. Share on Pinterest Some eyewear ...

Pupillary distance helps center your eyeglasses prescription. Your eyeglasses provider normally measures it for you, but you won’t find it on your prescription. If you order glasses online, you’ll ...