Patent GB-365660-A (GB)
Title: Improvements in sight testing apparatus
IPC: A61B3/06
Filed: 1930-10-28
Abstract: 365,660. Sight testing apparatus. PANK, H. G., 75, Rundle Street, Adelaide, Australia. Oct. 28, 1930, No. 32330. [Class 97 (i).] Apparatus for testing visual acuity, of the kind having a test object in the form of a split circle, is provided with a shutter having an opening adapted to pass across the test object so that a patient can be afforded either a continuous or a momentary view of the object. Means are also provided for testing colour perception and for testing the extent of the visual field. The apparatus comprises a part 1 carrying the test object &c. and a part 2 adjacent the patient by means of which he registers his impressions. The split circle is drawn on a rotatable disc 11 in front of which is a shutter 6 having an opening 7, and provided with operating means 9. The disc 11 can be turned by a handle 12. The handle 12 also acts as a switch arm co-operating with a series of eight contacts 20, Fig. 2, arranged in the circuits of eight lamps 23 equally spaced around a fixed disc 22 having apertures through which light can pass from the lamps, and also having an aperture 33 through which the test object can be observed. In front of the disc 22 is mounted a rotatable ring 24 having apertures 26 which register with the apertures in the disc 22, these apertures being covered by differently-coloured glasses. Additional apertures 26a may also be provided in the ring 24. Above the ring 24 is a small rotatable disc 29 having apertures 30, 31 which can be brought into register with the uppermost aperture in the ring. The apertures 30 are covered by coloured glasses and the apertures 31 are of diminishing sizes. The apparatus is also provided with a pointer 48 adapted to be rotated at a constant speed by an electric motor to indicate time on a dial 49. The part 2 of the apparatus also comprises a disc 53 having light apertures behind which lamps are mounted, this disc being arranged behind a rotatable ring 54 having holes 55, 55a covered by coloured glass. The disc 53 is also provided adjacent the lamps with sockets 62 adapted to receive a plug 64. In using the apparatus the operator turns the handle 12 to bring the split in the test object to any desired position and then operates the shutter release 9 to expose the object for the desired period of time. The release 9 is also arranged to operate a switch which sets the pointer 48 in motion. The patient having identified the position of the split in the circle inserts the plug 64 in the socket 63 corresponding to that position. The electrical circuits provided in the apparatus are such that if the identification is performed correctly the hand 48 stops and the lamps corresponding to the position of the arm 12, and therefore of the split in the circle, are illuminated. If the identification is incorrect no lamp is lighted and the pointer 48 continues to turn. In testing colour perception the arrangement is such that any desired colour can be exhibited on the apparatus 1 by the use of a single lamp 23 and the rotary disc 24. The lamps on the disc 53 are all illuminated and the patient is required to pick out on the disc 54 the colour which matches the exhibited colour. For testing the extent of the visual field the apparatus 2 is provided with a curved guide 71 on which is slidably mounted a box 80 carrying a test object 74. The patient looks through an axial aperture 66 in the disc 53 at an object 67 and the box 80 is displaced along its guide until the test object 74 enters the field of vision. A chin rest 87 is provided to fix the position of the patient's eyes. The guide 71 can be turned about the axis of the disc 53 to enable the test to be made in different meridians.