GB963094A - Improvements in or relating to ophthalmometers - Google Patents

Abstract

963,094. Ophthalmometers. SOC. ANON. GUILBERT ROUTIT & CIE. May 21, 1963 [May 22, 1962], No. 20221/63. Heading G2J. An ophthalmometer of the kind having two sighting marks which are projected on to the cornea of an eye under examination so as to form by reflection at the cornea images for observation through an eyepiece and having a beam splitting and beam combining system for duplicating the image of each sighting mark, is characterized by means for selectively rendering one or other of the sighting marks inoperative and control means adapted to enable the two images of the operative sighting mark to be linked to give the specific radius of curvature of the cornea at a particular point. Light from lamps 1a, 1b is projected through sighting marks A, B on to the cornea of the eye under test, and is reflected thereby through the objective 3 on to a beam splitting and beam combining arrangement of prisms 5, 6 whereby two images of each sighting mark are formed for viewing in an eye piece 13. Each sighting mark comprises a male and a female section so that the two images of one mark may be linked when the second mark is inoperative. The images are brought into coincidence by moving the mirrors 7, 8. The apparatus shown in Fig. 10 may be used in conjunction with the ophthalmometer to measure the radius of curvature of other surfaces, e.g. a lens. The lens is held, by suction, in the cup 45 which is rotatable about a horizontal axis to bring different points on the surface of the lens under examination, the angle of rotation being recorded by the pointer 54 on the scale 55. A mirror 56, inclined at 45 degrees to the horizontal, directs light rays from the surface of the lens to the ophthalmometer.