The next time you use a keratometer, you should know that earlier models, such as F.A. Hardy’s C.I. Ophthalmometer, made of enameled black cast-iron and decorative gold paint (a), was a precise instrument used to determine the amount and axis of astigmatism for eyeglass prescriptions. Patented in 1899 by John Chambers and Charles Inskeep, this device measured the curvature of the cornea much like a lens clock. The refractionist looked though the brass telescopic eyepiece to face the illuminated mires, which are located inside the black curved disc. The image of the mires (b) reflects on the cornea, made shiny by its tear film, allows for objective measurement of the anterior surface curvature of the two principal meridians. Whether you are fitting contact lenses, performing intraocular lens implant power calculations, or conducting corneal refractive surgery with today’s keratometer, think of how Chambers and Inskeep helped make those tasks possible! Courtesy of the Optical Heritage Museum, opticalheritagemuseum.com



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