On my prescription the dist pd is 31. This is not an option on the prescription so that i could enter my pd. Is that a normal measurment, if so Where or how do i enter this number?

Hello, dear staves. You said your prescription the dist pd is 31. I think that is normal! If there is not an option on prescription so that you could enter your pd, you could contact with the service and tell them your pd number. PD or pupilary distance is the exact measurement in millimeters from the center of one pupil to the center of the other while eyes are looking perfectly straight. This is very important factor of your prescription.