A new technique of eye-movement measurement based upon a photoelectric principle is described. An image of a small portion of the eye at the juncture of the iris and sclera is cast upon a surface containing a small horizontal slit. Behind the slit is located the photocathode of a photomultiplier tube. As the eye rotates on its vertical axis more or less of the sclera (or iris) falls upon the slit, and hence more or less total light reaches the photosensitive element of the tube. The output of the tube thus can be related directly to the angular position of the eye.
A system for generating a moving target whose velocity, displacement, form, intensity, and other characteristics can be varied systematically also is described. This system is coupled to that for measuring eye movements with the result that both the signal for eye movement and the signal for the movement of the stimulus can be displayed and recorded simultaneously on an oscilloscope. Consequently, both signals can be studied in detail as a function of time, and in relation to one another.
Eye movements of less than one degree can be measured with less than 10% error. Optical modifications of the present system will make possible the measurement of much smaller movements of the eye.
Extensions and improvement of the technique of measurement are discussed briefly.
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