A graphical calibration method of three dimensional eye position recordings

In the graphical method proposed the calibration is made by means of a dot moving on a projection screen along the corners of an ideal square 40 deg wide. The eye movements are measured by serch coil system. Plotting the recorded data in bi-dimensional graph, with the horizontal position on the x-axis and the torsion values on the y-axis, an X-shaped figure is obtained. From Listing's law the crossing point of the two tracks gives the horizontal coordinate of the primary position. By repeating the same procedure for the vertical and torsion values the vertical coordinate of the primary position is measured. The recorded data give also the horizontal and vertical amplitude of the signal related to 40 deg eye movements.