Sources of artifact in infrared recording of eye movement

A detailed analysis of recording artifacts present in normal horizontal saccadic eye movements was performed using infrared reflective oculography. The effects of diode displacement were assessed. Optimal recordings were obtained with infrared sensors displaced 1 mm scleral to the midlimbal position. Displacement of the infrared sensor toward the sclera resulted in an artifactual decrease in apparent peak saccadic velocity. Displacement of the infrared sensors toward the pupil resulted in complex nonlinear waveforms. Such artifacts were more apparent with increasing eccentricity of the eyes from primary position. The artifacts induced by poor positioning of the sensors were readily explained by changes in infrared reflectivity among sclera, iris, and pupil. Simultaneous independent recording from temporal and nasal sensors was recommended to separate truly anomalous saccadic trajectories from artifact.