Pupillary distance, usually written as PD, is the distance in millimeters used to help position the optical centers of eyeglass lenses. It is a fitting measurement rather than the sphere, cylinder, axis, or add portion of the prescription.
A single PD gives one total measurement across both eyes. A dual PD gives separate right and left measurements from the center of the nose. Dual values can be useful when facial measurements are not symmetrical.
Incorrect PD can place the usable lens area away from where the eyes naturally look. The effect can be more noticeable with stronger prescriptions, multifocal lenses, or frames that sit differently from the position used during measurement.
Use a measurement from an eye-care or optical record when available. If measuring at home, repeat the measurement and follow the seller's instructions carefully; do not guess or substitute a frame measurement for PD.
Shop frames