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Cost: Progressive lenses are more expensive than bifocal and single-vision lenses due to higher manufacturing and fitting costs. Some research has been conducted to reduce the fabrication cost by precision injection molding. [6]
The add segment of the lens for near vision is the D-shaped area. A bifocal is a lens with two sections, separated by a line (see image to the right). Generally, the upper part of the lens is used for distance vision, while the lower segment is used for near vision. The area of the lens that caters to near vision is called the add segment.
Distance vision corrections are made by re-adjusting the lens for distance, instead of by tilting and/or rotating the head to view object through the best part of the lens for the distance. Adjustable focus lenses, like single-focus lenses, also reduce image-jump and spatial distortion in the field of view associated with traditional multi ...
This specifies the part of the prescription designed primarily to improve far vision. In a bifocal lens, this generally indicates what is to be placed in the top segment. NV is an abbreviation for near vision. This may represent a single-vision lens prescription to improve near work, or the reading portion of a bifocal lens.
Stage-by-stage, he experiences the vision produced by single-vision and bifocal lenses, and then that of standard progressive lenses, and ultimately Varilux lenses. The world premiere of Varilux Experience marked Varilux's 50th anniversary and took place at the SILMO optical trade fair, which ran from October 30 to November 2, 2008, at Paris ...
Like other lenses for vision correction, aspheric lenses can be categorized as convex or concave. Convex aspheric curvatures are used in many presbyopic vari-focal lenses to increase the optical power over part of the lens, aiding in near-pointed tasks such as reading. The reading portion is an aspheric "progressive add".
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