Test types (Orthops)

Catalogue Number: 1728
Test types (Orthops)
Category: Equipment
Sub-Category: Reading card, tests of near vision
Time Period: 1900 to 1939
Description Of Item: Near vision test card printed on light brown stiff card and framed in a timber frame 145 x 290 mm, headed 'TEST TYPES Orthops' with blocks of words of differently sized typeface labelled No 1 to No 12 from smallest to largest. Under each of the numerical size designations is a lens power from 0.25 D for the smallest line to 3.00 D for the largest. On the reverse is printed a vertical line passing through a black dot 8 mm in diameter.
Historical Significance: The numbers No 1 to 12 are probably Jaeger type sizes. In Laurance's book on visual optics and sight testing 1912 he states on page 72 in his description of reading types that in addition to the Jaeger Number, reading types have also the power of a correcting lens that will enable reading of type size No 1 when the designated type size is the smallest legible. Orthops is the description of a subjective sight testing chart designed by Laurance that includes a fan dial, Snellen test letters and a red green tangent scale. See illustration facing page 213 of Laurance's book. Since it carried the othops name this near chart may have been designed by Laurance.
Condition: Good
Location: Archive room. West wall. Unit 2 Drawer 2

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