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A corrective lens is a transmissive optical device that is worn on the eye to improve visual perception. The most common use is to treat refractive errors: myopia, hypermetropia, astigmatism, and presbyopia. Glasses or "spectacles" are worn on the face a short distance in front of the eye.
www .zennioptical .com. Zenni Optical (formerly 19dollareyeglasses.com) is an American online retailer of prescription glasses and sunglasses. Founded in 2003 by Tibor Laczay and Julia Zhen, it is based in Novato, California . The company sells more than 2,000 types of prescription glasses and sunglasses but does not sell contact lenses.
The template for rimless eyeglasses date back to the 1820s, when an Austrian inventor named Johann Friedrich Voigtländer [ de] marketed a rimless monocle. [2] The design as it is known today arose in the 1880s [3] as a means to alleviate the combined weight of metal frames with heavy glass lenses. The style also came about from a desire to make eyewear as inconspicuous as possible; [4] at the ...
The most common type of corrective lens is "single vision", which has a uniform refractive index. For people with presbyopia and hyperopia, bifocal and trifocal glasses provide two or three different refractive indices, respectively, and progressive lenses have a continuous gradient. [1]