SACCADOMETER - The Saccadometer Plus system measures eye movements in horizontal axis with temporal 1kHz and spatial resolution < 5 arc min. The system incorporates a built in visual target presentation using miniature laser projectors mounted on the sensor forehead plate. Saccadometer Plus is equipped with three red laser projectors with 10º separation, and 6 experiments are included in embedded software.The information about the eye movement is stored in a small, self-contained control unit, and can be downloaded for computer analysis at a later stage.Information about eye movement is acquired by analyzing the infrared light reflected from eye orbit. The left and right eye orbit are illuminated by two infrared LEDs, providing eye surface irradiance below 1mW/cm 2 (operating condition). Due to the conjugacy and synchronicity of the saccadic eye movements, the rotation of left and right eyes, can be added and averaged. The inner canthi of the left and right eyes are illuminated with the low intensity IR. The difference between the amounts of IR reflected back from the eye surfaces toward the photodetecting circuitry, carries the information about the eye position changes. Two eye landmarks are taking part in generation of the eye movement signal: the corneal bulge and the limbus (the border between darker iris and white sclera). Main contributor to the eye movement signal is the corneal bulge. Being the relative eye position measurement system, it requires to define the initial eye position. It means that at the beginning of every measurement, a steady eye fixation point needs to be provided. In Saccadometer the central fixation target serves this purpose.
2017-01-26