Figure 5.

Geometric correction. (A) Simulation of the eye looking straight ahead. (B) Simulation of the eye looking 50° to the side. (C) Iris pattern corresponding with the eye looking straight ahead. (D) Iris pattern corresponding with the eye looking 50° to the side applying the geometric correction. (E) Iris pattern corresponding with the eye looking 50° to the side without applying the geometric correction (note the distortion on the pattern). (F) Average torsion error as a function of eccentricity in simulated eye movements calculated with and without geometric correction. Note that even though the degradation of the signal with eccentricity is gradual, the accuracy breaks down at about 35° when other peaks in the cross-correlation reach a similar height as the main peak. (G) Example of torsion in response to head rolling (left eye in blue and right eye in red) recorded at an eccentric horizontal gaze position with geometric correction (middle) and without geometric correction (bottom).