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Wichterle thought pHEMA might be a suitable material for contact lenses and gained his first patent for soft contact lenses. In 1954 this material was first used as an orbital implant. In 1957 Wichterle produced around 100 soft lenses from closed polystyrene molds but the edges split and tore as the lenses were removed. In addition, they ...
Multifocal contact lenses (e.g. bifocals or progressives) are comparable to spectacles with bifocals or progressive lenses because they have multiple focal points. Multifocal contact lenses are typically designed for constant viewing through the center of the lens, but some designs do incorporate a shift in lens position to view through the ...
A torus results when a circle with radius r rotates around an axis lying in the same plane as the circle (here the z axis) at a distance R from the centre of the circle.. A torus is the surface of revolution resulting when a circle with radius r rotates around an axis lying within the same plane as the circle, at a distance R from the circle's centre (see figure at right).
Orthokeratology lens. Orthokeratology, also referred to as Night lenses, Ortho-K, OK, Overnight Vision Correction, Corneal Refractive Therapy (CRT), Accelerated Orthokeretology, Cornea Corrective Contacts, Eccentricity Zero Molding, and Gentle Vision Shaping System (GVSS), is the use of gas-permeable contact lenses that temporarily reshape the cornea to reduce refractive errors such as myopia ...
Chinon Industries Inc. (チノン株式会社, Chinon Kabushiki-gaisha) was a Japanese camera manufacturer. Kodak took a majority stake in the company in 1997, and made it a fully owned subsidiary of Kodak Japan, Kodak Digital Product Center, Japan Ltd. (株式会社コダック デジタル プロダクト センター, Kabushiki-gaisha Kodakku Dejitaru Purodakuto Sentā), in 2004. [1]
A simplest case is where thin lenses are placed in contact (=). Then the combined focal length f of the lenses is given by = +. Since 1/f is the power of a lens with focal length f, it can be seen that the powers of thin lenses in contact are additive. The general case of multiple thin lenses in contact is