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The VPS is a non-invasive ultrasonic device intended to measure the pattern of eye and head movement when viewing lateral visual stimulus, to use as a guide for prescribing progressive power eyeglass lenses.

The VPS is a non-invasive ultrasonic device intended to measure the pattern of eye and head movement when viewing lateral LED fixation lamps. It consists of a headset and a main body with an ultrasonic transmitter. Two ultrasonic receivers are imbedded in the center nosepiece of the headset. The patient wears the headset and looks at three orange LED fixation lamps in the main body as they light up in succession. As the patient follows the lights from side to side, the device measures the degree of head movement from the center light against a target angle of 40° and a standard deviation. Eye movement is extrapolated to fill the remaining vision angle. The calculated ratio of head/eye movement is used to determine the shape of the peripheral and central fields of the progressive spectacle lenses.