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Learn about the different types of optical prisms, such as dispersive, reflective, beam-splitting and polarizing prisms, and how they refract, reflect or split light. Find out how prisms are made of transparent materials like glass, acrylic or fluorite, and how they can create spectra, images or polarizations.
Prentice's rule is a formula to calculate the amount of prism correction in a lens based on decentration and lens power. It can be used for prescribing, tolerance control, or determining unprescribed prism in eyeglasses.
Optical glass is a type of glass suitable for optical systems such as lenses, prisms or mirrors. It contains additives to modify its optical or mechanical properties, such as refractive index, dispersion, transmittance and thermal expansion.
Adjustable focus eyeglasses have one focal length, but it is variable without having to change where one is looking. Possible uses for such glasses are to provide inexpensive eyeglasses for people from low-income groups , developing countries , third world countries or to accommodate for presbyopia.
A progressive lens is a corrective lens used in eyeglasses to correct presbyopia and other disorders of accommodation. It has a gradient of increasing lens power from top to bottom, and can provide clear vision at different distances. Learn about its history, design, advantages, disadvantages and adaptation.
Bifocals are eyeglasses with two distinct optical powers, commonly prescribed to people with presbyopia. Benjamin Franklin is generally credited with the invention of bifocals, but there is some evidence that others may have come before him.