Greens Refractor Directions for use

Historical Significance: Refractors 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 lenes in steps of power of 0.25D, with the axis of the sylindrical 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 1950s 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 (see picture page A57 in Hisrchberg's History of Ophthalmology Vol II Part 2).