Petra Glasses

Progressive

This refers to the lens design which includes three fields of vision, without lines, and is sometimes referred to as a " no-line multi-focal ".

In a progressive lens, the shape of the corrected part of the lens is approximately that of a funnel or a mushroom. The top portion is for distance-vision, narrowing to the lower middle for mid-range, and finally to the bottom portion for the near-vision or reading. The reading area is expected to be smaller than the distance area. People sometimes prefer a single-vision lens for extended reading or up-close work.

The lens height for a progressive lens must be 33mm or greater. We recommend a taller lens for more comfortable wear, but the minimum lens height is 33mm. If this frame has a lens height smaller than 33mm, a different frame must be chosen for progressive lenses.

What is Rx range?

Rx is customarily part of the superscription of a prescription, for a patient to purchase a prescription drug from a pharmacist. It can only be made in certain prescriptions. This is an approximate range based on the spherical (SPH) value.

Please be noted:

If you have astigmatism (CYL) in your prescription, this range may be further limited. Please enter your prescription on the order page to check whether the glasses are suitable for you.

PD Range

Pupilary 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 fnd out how to measure it here.