Eye movements are either spontaneous in nature or they are visually guided.
Some conventional eye-trackers are not fast enough to distinguish different types of movement and most incorporate ferrous materials and electronics that are incompatible with magnetic environments. These photodiodes are coupled to an amplifier, which provides independent estimates of the horizontal and vertical positions in one eye. The system works with a daylight suppression technique, to prohibit interference from ambient light. The fibre optic cables are encased in black malleable plastic for easy handling and their long length prevents the MR-Eyetracker Control Unit from interfering with the magnetic field. The ends of the cables are mounted into a custom eyepiece that is attached directly to the head coil.