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Varilux. Varilux is a brand name belonging to Essilor International, a producer of corrective lenses. The first version of the lens was invented by Bernard Maitenaz and released in 1959, and was the first modern progressive lens to correct presbyopia. The progressive lens is characterized by correcting near, intermediate and far vision.
Progressive lenses are corrective lenses used in eyeglasses to correct presbyopia and other disorders of accommodation. They are characterised by a gradient of increasing lens power, added to the wearer's correction for the other refractive errors. The gradient starts at the wearer's distance prescription at the top of the lens and reaches a ...
The US Food and Drug Administration (FDA) defines soft contact lenses as: made of soft, flexible plastics that allow oxygen to pass through to the cornea. Soft contact lenses may be easier to adjust to and are more comfortable than rigid gas permeable lenses. Newer soft lens materials include silicone-hydrogels to provide more oxygen to your ...
After many years as rivals, Essel and Silor merged on 1 January 1972 to form Essilor, then the world's third-largest ophthalmic optical firm. [1] Its first year of existence was marked by the creation of Valoptec, a non-trading company composed of stockholder managers who held half the company's capital stock, and the purchase of Benoist-Bethiot, a French lens manufacturer specializing in ...
Converting units of temperature differences (also referred to as temperature deltas) is not the same as converting absolute temperature values, and different formulae must be used. To convert a delta temperature from degrees Fahrenheit to degrees Celsius, the formula is {ΔT}°F = 9 5 {ΔT}°C. To convert a delta temperature from degrees ...
Comparison of platform virtualization software. Platform virtualization software, specifically emulators and hypervisors, are software packages that emulate the whole physical computer machine, often providing multiple virtual machines on one physical platform. The table below compares basic information about platform virtualization hypervisors.
16:9. 8,294,400. 7680 × 4320. 8K UHDTV. 4320p. 33,177,600. Many of these resolutions are also used for video files that are not broadcast. These may also use other aspect ratios by cropping otherwise black bars at the top and bottom which result from cinema aspect ratios greater than 16∶9, such as 1.85 or 2.35 through 2.40 (dubbed ...
The following is a comparison of e-book formats used to create and publish e-books . The EPUB format is the most widely supported e-book format, supported by most e-book readers except Amazon Kindle [a] devices. Most e-book readers also support the PDF and plain text formats. E-book software can be used to convert e-books from one format to ...