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, 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 36mm or greater. We recommend a taller lens for more comfortable
wear, but the minimum lens height is 36 mm. If this frame has a lens height smaller than 36mm, a different frame
must be chosen for progressive lenses.