GB605266A - Improvements in devices for testing eyesight - Google Patents

Abstract

605,266. Sight-testing devices. HEALY, J. R. June 6, 1945, No. 15019. [Class 97 (i)] The device comprises two annular bands of transparent material having several lens sections thereon which on one side are each formed with spherical surfaces and on the other side with cylindrical surfaces of progressively varying radii, the bands being mounted with their axes orthogonal and one within the other with their spherical surfaces adjacent so that each may be rotated about its own axis to bring together two overlapping lens sections which can be presented like a spectacle lens before the eye to be tested. As shown a bowl 12, which is a minor segment of a sphere, has formed thereon an annular band 13, the inner surface of which is spherical while the outer surface thereof is cylindrical and has a curvature varying in steps. Within the bowl 12 and disposed with its axis orthogonal thereto'is a similar bowl 14 having an annular band 15, the outer surface of which is spherical while the inner cylindrical surface has a curvature varying in steps. At the pole or each bowl is a spindle, mounted in bearings in a frame 16, so that each bowl may be rotated about its own axis ; this frame may be provided with a pointer co-operating with an index on the annular band to indicate the focal powers of the lens sections in front of the eye. The frame may also be provided with scales and be rotatable about the line of sight so that a cylindrical connection may be determined when necessary. Each bowl and annular band may be formed from plastic material such as polymethyl methacrylate.