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The Varilux Physio progressive lens is characterized by an improvement in colour contrast and wider fields of vision. It derives its performance from a patented innovation called the Twin RX Technology which combines a method for calculating lens optics, Essilor's Wavefront Magement System and advanced digital surfacing. [ 24 ]
The Carl Zeiss AG & Varilux lenses were the first PAL of modern design. Bernard Maitenaz, patented Varilux in 1953, and the product was introduced in 1959 by Société des Lunetiers (now Essilor). The first Varilux lenses' surface structure was however still close to a bifocal lens, with an upper, aberration-free half of the surface for far ...
Near visual acuity or near vision is a measure of how clearly a person can see nearby small objects or letters.Visual acuity in general usually refers clarity of distance vision, and is measured using eye charts like Snellen chart, LogMAR chart etc. Near vision is usually measured and recorded using a printed hand-held card containing different sized paragraphs, words, letters or symbols.
For 6/6 = 1.0 acuity, the size of a letter on the Snellen chart or Landolt C chart is a visual angle of 5 arc minutes (1 arc min = 1/60 of a degree), which is a 43 point font at 20 feet. [10] By the design of a typical optotype (like a Snellen E or a Landolt C), the critical gap that needs to be resolved is 1/5 this value, i.e., 1 arc min.
Corrective lenses provide vision correction over a range as high as +4.0 diopters. People with presbyopia require a convex lens for reading glasses; specialized preparations of convex lenses usually require the services of an optometrist. [15] Contact lenses can also be used to correct the focusing loss that comes along with presbyopia.
The Micro Four Thirds system (MFT) of still and video cameras and lenses was released by Olympus and Panasonic in 2008; lenses built for MFT use a flange focal distance of 19.25 mm, covering an image sensor with dimensions 17.3 × 13.0 mm (21.6 mm diagonal).
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