Device for the investigation of the field of view of the human eye

摘要

925,066. Sight-testing apparatus. A. J. FRIEDMANN. Jan. 18, 1962 [Feb. 1, 1961], No. 1932/62. Class 97 (1). For testing the field of vision, a housing has means for accommodating a perforated screen means and a light source for momentarily illuminating the perforations, means being provided for changing the position or pattern of perforations and for identifying the pattern in use at any instant. As shown in Fig. 1, the housing 1 contains an electronic flash tube 3 for illuminating perforations in a screen 5, which is slidably inserted in guides 1a and has a central pivot 7 on which a perforated shutter 6 is rotatable between angular positions defined by a spring 9 and arcuate detent 8. For each angular position of the shutter 6, a different group of perforations are lit up by operating the flash tube 3. By using a scale 11 and index 10 the blind spots in the patient's field of vision can be plotted; scale 11 may indicate not only which perforation group is exposed but also the number of perforations in that group. Instead of using an electronic flash tube, the source may be flickering or continuous, a shutter being interposed in the light path to the screen in the latter case. In a modification, Fig. 5, a perforated circular screen 17 is rotatable and has rotatably secured thereto at 7 a shutter 6 which is also perforated. The scale and index 11, 10 are again provided and, in addition, there is an index mark 41 co-operating with a scale 42 to indicate the angular position of screen 17. This modified instrument allows additional tests to be performed using the same group of perforations at different angular orientations. In other forms, the rotatable and circular screen is provided with a series of perforations along one radius only and the shutter has an arcuate set of holes or an arcuate slit so that only one perforation is exposed at a time. In yet another modification, Fig. 9, a number of perforated cards 43 are locatable in the guides la, each card having a group of perforations 45 and a pattern identifying mark 46.