Catalogue Number: 4054
Category: Equipment
Sub-Category: Contact lens equipment
Time Period: 1940 to 1999
Place Of Publication/Manufacture: Japan
Publisher/Manufacturer: Shin-Nippon
Description Of Item: Used to measure the back curvature radius of rigid contact lenses. This instrument has a grey metal body with a vertical travelling microscope, a horizontally mounted light source, a dial with adjustable knobs and a side mounted micrometer. Eyepiece of microscope is 10x, objective 5x with total magnification 50x. An adjustable circular plate with holder for contact lenses sits under the microscope. Marked SNC SHIN-NIPPON TOKYO JAPAN NO. 21364 on front of unit. Overall size 44cm (H), 220mm (D), 15 (W).See also Catalogue No. 1794
Historical Significance: The radiuscope uses the Drysdale principle to determine the base curve of rigid contact lenses i.e. by using convex, concave, and plane mirror reflection. The real image is formed at the first focal plane and an aerial image formed at the second focal plane. The vertical distance between two images represents the radius of curvature of the lens.Radiuscopes were used widely in all contact lens labs to measure the posterior surface curvature of rigid contact lenses. They are also used by eyecare professionals to verify the accuracy and quality of contact lenses.
How Acquired: Donated by Peter Nixon
Date Acquired: 13/03/21
Condition: very good
Location: Archive office. East wall shelves unit 2

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