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A rare Victorian-era optometer device patented by George Johnston of Detroit, Michigan in 1882. This device was used to determine the strength of lenses needed for eyeglasses by measuring refractive error and was a precursor to the modern Phoropter. The piece is comprised of steel and brass is of a mostly spherical shape. Inside the sphere is a set of rotating, overlapping rings with many small lenses along their circumference. The patient would peer through a small hole on one side of the sphere and the optometrist would make adjustments to the internal lenses until the patient’s vision was clear. The other side has a long telescoping viewing tube which would be extended when in use.
America, ca. 1882.
Extended length: 14 3/4 in., (37.5 cm.)
Condition: Good overall, with expected signs of age and use.
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