DEVELOPMENT OF A 3- ROD-APPARATUS CONTROLLED BY COMPUTER FOR DETERMINING THE STEREOSCOPIC THRESHOLD

97th DOG Annual Meeting 1999

K478
DEVELOPMENT OF A 3- ROD-APPARATUS CONTROLLED BY COMPUTER FOR DETERMINING THE STEREOSCOPIC THRESHOLD

M. Kartscher, G.O. Bastian

We present an instrument that combines the psychophysical method for depth sight threshold determination by a 3-rod-divice and modern computer technology. Results can thus be reached significantly faster than before. We can determine three pairs of thresholds within 5 minutes of average.

Method: We worked with a modified version of the apparatus by Bastian and Kegel (1). It is a 3-rod-apparatus situated at 36 cm from the experementee. The two outer rods are fixed. The middle rod is fixed on a micrometric screw driven by a stepping motor for forward and backward movements. By random selection, front and rear limit of the depth sight threshold are determinded by means of converging method. In each test stage we get three stereoscopic tresholds per experementee. We tested 103 experementees. 38 of them repeated the test after some time in order to document the reproducibility of the results.

Results: By above mentiond method, the tests at our apparatus showed a good reproducibility. The average threshold dimension is situated at 11" (seconds of arc), the lowest at less than 1" and the highest at 54". A fluctuation of the thresholds and of the physiological zero position can be shown.

Resume: In principle, the apparatus is suited for short distance mass screening of depth sight thresholds, though quantitative testing of stereoscopic vision rather plays a minor role in practice. Nevertheless, this apparatus is a valuable addition for further sensoryphysiological tests because of the little space it takes as well as of the very short test durations.

1. G.O. Bastian, J. Kegel: Fortschr Ophthalmol (1989) 86: 387-391

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