Greens refractor head

Historical Significance: Refractors (=phoropters) developed in the 1920s from the phorometer. The phorometer was in essence a trial frame designed to be suspended in front the patient from an arm off an instrument stand. It had the convenience of carrying pairs of Jackson cross cylinder, Risley prisms and Maddox rods so these did not have to fetched from a trial case and inserted in the trial frame. The next step was to incorporate rotating discs carrying spherical and cylindrical lenses in steps of power of 0.25D, with the axis of the cylindrical lenses being rotatable. A number of optical instrument companies made phorometers and refractors but the Green's refractor was one that attained great popularity in the 1930s to the 1970s because of its ease of use and reliability. It was designed by AS Green MD, LD Green MD, and MI Green MD of San Francisco (see Cat No 1719 for a Bausch and Lomb Catalogue dated 1936 for a full description of the instrument). The patent for the Greens refractor was lodged in 1929 and granted in 1932. (see picture page A57 in Hirschberg's History of Ophthalmology Vol II Part 2). The first Greens were produced in 1934. The Museum has a manual for it dated 1935. (Cat No 1223). The early Greens refractor heads were made with a black crackle finish. The Greens refractor remained essentially unchanged during the four decades of its production and remained in use into the 21st century . The Kett Museum has several Greens refractors, some of which date to the late 1930s. Production of the Greens refractor stopped in the late 1970s in the face of competition from the AO Ultramatic and Japanese manufacturers