Vertometer was the trade name of an instrument made by Bausch & Lomb

Bausch & Lomb

Bausch & Lomb, an American company based in Rochester, New York, is one of the world's leading suppliers of eye health products, such as contact lenses and lens care products today. In addition to this main activity, in recent years the area of medical technology has been developed...

 (B&L) and later by Reichert

Reichert

Reichert may refer to:* Alexander Julius Reichert, mayor* Benjamin Reichert, footballer* Craig Reichert, ice hockey player* Dan Reichert, baseballer* Dave Reichert, politician* Don Reichert, artist* Isabel Reichert, artist...

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Lensometer was the trade name of the nearly similar instrument made by American Optical.
Neither the Vertometer or the Lensometer is now being made.
Lensmeter

Lensmeter

A lensmeter or lensometer, also known as a focimeter, is an ophthalmic instrument. It is mainly used by optometrists and opticians to verify the correct prescription in a pair of eyeglasses, to properly orient and mark uncut lenses, and to confirm the correct mounting of lenses in spectacle frames...

 is a generic name that can be applied to any lens measuring instrument.
'A vertometer is an ophthalmic bench instrument used to measure dioptric power of a lens. It differs from a lensmeter

Lensmeter

A lensmeter or lensometer, also known as a focimeter, is an ophthalmic instrument. It is mainly used by optometrists and opticians to verify the correct prescription in a pair of eyeglasses, to properly orient and mark uncut lenses, and to confirm the correct mounting of lenses in spectacle frames...

 or lensometer which is a general dispensary tool for opticians

Optician

An optician is a person who is trained to fill prescriptions for eye correction in the field of medicine, also known as a dispensing optician or optician, dispensing...

 to verify spectacle prescriptions at the laboratory. A vertometer, on the other hand, is a more precision instrument used to locate, mark, and index a lens optical center for edging, mounting, and construction of a spectacle

Glasses

Glasses, also known as eyeglasses , spectacles or simply specs , are frames bearing lenses worn in front of the eyes. They are normally used for vision correction or eye protection. Safety glasses are a kind of eye protection against flying debris or against visible and near visible light or...

 prescription

Eyeglass prescription

An eyeglass prescription is an order written by an eyewear prescriber, such as an optometrist or ophthalmologist, that specifies the value of all parameters the prescriber has deemed necessary to construct and/or dispense corrective lenses appropriate for a patient.If an examination indicates that...

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History

The theory of geometrical optics uses ray tracing techniques. In many of his models, Galileo used a mathematical formula that measured a vertex distance. This nomenclature prevailed throughout hundreds of years, during a time that studies of optics may have been misunderstood. Derived from the word, the measure of the focal length of a lens is represented by the reciprocal of the vertex distance in meters, or diopters. Vertometers measure sphere ± cylinder x axis, and can be used to calculate prismatic power by indexing the optical center offset from the visual axis. An ink coated stylus is used to mark optic centers on the lens in the optical laboratory. A millimeter rule would be nearby for spectacle eyesize fittings.