Pupillary Distance (PD) is the distance, in millimeters, between the center of one pupil to the center of the other. The PD is needed to manufacture your eyeglasses because it determines the exact optical center of the lens, which is the point where you look through the lens. PD is especially important for manufacturing progressive lenses.

Once you have your PD, you can upload your photo to the Frame Fit tool and begin trying on glasses. The Frame Fit tool allows you to see exactly what the glasses look like on you and how well they fit the size and shape of your face. If you don’t have your PD, you can find out how to measure it here.

Prism is a measure in prism diopters. The most common application for this is the treatment of strabismus. In eyeglasses, prisms are used primarily for double vision, positional correction, or convergence correction. By moving the image in front of the deviated eye, double vision can be avoided and comfortable binocular vision can be achieved.

A lens which includes some amount of prism correction will displace the viewed image horizontally, vertically, or a combination of both directions. Ublins is able to accommodate prism corrections with a range of 0 to 5.00 diopters in any direction or combination of directions. In an eyeglass prescription, the base is typically specified as up, down, in, or out. Prism corrections are available only for single-vision prescriptions, not progressives.