When purchasing a pair of eyeglasses online, you will need to provide your pupillary distance (PD). Normally the pupillary distance can be provided by a local optometrist or measured by a PD ruler online. Within the United States, there are only 3 states that require the eye care professionals to include the PD within the RX prescription: Alaska, Massachusetts, and New Mexico.
The other states are not required to provide this information, but this measurement can still be requested from the optometrist. This infographic shows a map of the US States that require PD in the prescriptions.
Embed This Image On Your Site (copy code below):