Acquisition of subject’s eye movement during the exploration of the graphical interface is made by using a videooculographic device (EyeGaze, LC Technologies Inc., Fairfax, Virginia).

The EyeGaze is a “remote” system composed of a video camera mounted below the computer screen, and a video monitor allowing to control that the subject’s eye is focused and centred within the camera field. The system uses the Pupil-Centre/Corneal-Reflection (PCCR) method to determine gaze direction. A small infrared light emitting diode illuminates the eye and generates a very bright reflection on the cornea. This effect enhances the camera’s image of the eye and is used by the image processing algorithms to locate the centre of the pupil. The software calculates the co-ordinates of gaze position based on the relative positions of the pupil centre and corneal reflection within the video image of the eye. The basic feature of the system is that no contact exists between the recording device and the subject and therefore no discomfort is caused even by very long acquisition sessions.