A lens with two fields of vision separated by a line. Generally the top is designated for distance-vision or computer-distance and the bottom for near-vision work such as reading.
In a Bifocal lens, the two fields of vision are specifically differentiated by a visible line. The bottom reading area is 28mm wide and is positioned just below the centerline of the lens. The physical position of the bi-focal area will be affected by the physical height of the lens chosen.
The total lens height for a Bifocal lens must be 30mm or greater. We recommend a taller lens for more comfortable wear, but 30 mm is the minimum height for a bifocal lens. If the frame chosen has a lens height smaller than 30mm, a different frame must be chosen for Bifocal lenses.
This refers to the lens design which includes multiple 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.
In a Standard Progressive, the top portion is for distance-vision, narrowing to the lower middle for intermediate-vision, finally to the bottom portion for the reading-vision. The intermediate and reading areas are expected to be smaller than the distance area. Standard Progressives are the most commonly worn progressive lenses.
In a Workspace Progressive, the top portion is for intermediate vision, while the bottom portion is for near-vision or reading; there is no distance vision in a Workspace Progressive. There are 2 types of Workspace Progressives: the Mid-Range Progressive, and the Near-Range Progressive. The Mid-Range Progressive is suitable for near work that involves heavy intermediate vision such as desktop computers and meetings, while the Near-Range Progressive is best for stationary near work such as prolonged reading, hand-held device use, and crafting.
The lens height for a progressive lens must be 30mm or greater. We recommend a taller lens for more comfortable wear, but the minimum lens height is 30 mm. If this frame has a lens height smaller than 30mm, a different frame must be chosen for progressive lenses.