LOOKING BACK – APRIL 2010

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19TH CENTURY REFRACTIVE ERROR MEASUREMENT

Patented in December 1895, inventor Henry L. DeZeng, Jr.’s new refractometer was touted for enabling an ECP to measure the human eye’s refractive errors quickly and accurately without the assistance of a mydriatic drug (as seen in the 1897 Optical Journal advertisement above).

Manufactured by Cataract Optical Co. in Buffalo, NY, the DeZeng Refractometer was constructed of nickel-plated brass and cast iron and consisted of a tube 8.5 in. x 2.125 in. mounted on a bracket pivoted to an upright pillar to allow for horizontal or oblique adjustment. Sliding within the main tube was an inner tube constituting a lens carrier. Two rotating wheels of lenses at the front permitted a range of cylindrical power from 0.12D to 8.75D. As a patient looked through the DeZeng Refractometer at a test card hanging 15 ft. or 20 ft. away, a number of convex or concave lenses could be placed before the eye by simply rotating the wheel.

The selling price for this new instrument was $60, a substantial investment at the time for doctors who wanted to give an accurate vision assessment.



Courtesy of The Archives & Museum of Optometry, St. Louis, MO.

 

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