GB730484A - Improvements in or relating to hand ophthalmoscopes - Google Patents

Abstract

730,484. Sight-testing apparatus. KEELER, C. H. Sept. 16, 1953 [Sept. 17, 1952], No. 23392/52. Class 97 (1). A hand opthalmoscope comprises a handle containing an electric lamp bulb and a battery to direct a vertical light beam into a head mounted on the top of the handle and having a mirror arranged at substantially 45 degrees to the illuminating beam to reflect it into the patient's eye, light-transmitting means adjacent the mirror to direct light reflected from the eye past the mirror to a viewing aperture, polarizing means movable into the illuminating beam and an analyser mounted on an actuating member so as to be movable into or out of the beam reflected by the eye. As shown in Fig. 3, light from the lamp passes a condenser 14, an iris diaphragm 15 and a slit diaphragm 16 to reach the head 12. The diaphragm 16, Fig. 6, is formed of two plates 38, 39 slidable in a groove 37, the width of the slit 40 therebetween being varied by rotation of a plate 34 having curved slots 41, 42, engaging pins 43, 44 respectively .on the plates. Light emerging from this slit reaches a turret device 18, Eig. 4, rotatable to 'locate a circular strip 58, a negative lens 60 or stops 62, 63 in the beam before it reaches an objective 19. Light from the objective reaches a curved carrier 26 movable to locate therein a clear hole 69, a polarizing-screen 70, a negative lens 71 or a red-free filter 75. The light is then reflected by an inclined mirror 20, Fig. 3, through an aperture 21 to reach the patients eye, the light reflected thereby passing to the viewing aperture 23 by way of a transparent patch 22 in the mirror 20. Rotatable on a spigot 92, Fig. 3, is a turret 24 by which one of a number of lenses 81 may be located before the viewing aperture, a further series of lenses 90 being similarly mounted on a turret 25 rotatable about a spigot 91 being also movable before the' viewing aperture. The turret 24 also carries a number of apertures containing transparent material indicating the power of the lens 81 located over the viewing aperture, this indication being seen in a lens 88 by light diffusely reflected in the interior of the head by a transparent plate 84 inclined to the illuminating beam. Also rotatable on the spigot 92 is an arm 93 bearing an analyser 27 which, by rotation of the arm may be moved over or away from the viewing aperture. The aperture 21 is internally screw-threaded to receive a negative lens for the examination of highly myopic patients, a scleral illuminator of convergent funnel-like form carrying condensing lenses, or a cobalt blue filter for fluorescein examinations.