Improvements in Apparatus for Enabling the Observer to Ascertain and Measure certain Defects in Vision and to View, Delineate and Measure Entoptic Phenomena.

摘要

24,162. Barrett, W. F. April 29, 1908. Sight-testing apparatus. - The apparatus described in Specification No. 21,742, A.D. 1905, is supplemented by the following accessory fittings. (1) A pair of tubes, Fig. 6, each with a transparent bottom, the larger one of which is partly filled with some coloured liquid, into which the smaller tube is more or less depressed to adjust the thickness of the coloured stratum through which vision occurs when testing the light and colour sense ; the inner tube may carry a lens and test diagram. (2) A device, Fig. 7, for simultaneously presenting and superposing differently coloured screens, one placed at X and the other at X1, the former being seen directly and the latter by reflection in a transparent plate N. (3) A device, Fig. 8, for securing in testing operations the at-rest condition of the eye, consisting of a viewing-lens P over which a reflector N is mounted to present simultaneously to the eye with the test diagram some distant object and thus secure the required adjustment of the eye.