The ocular stress monitor: a new device for measuring discomfort glare

Discomfort glare is always accompanied by a strong contraction or spasm in the muscles surrounding the eye. A portable device for measuring the electrical activity generated by this muscle spasm is described. The device samples the signal from electrodes placed around the eye. It is composed of a narrow-band amplifier/transmitter, a receiver/frequency converter and a tone generator. The signal amplitude is proportional to the vertical illuminance at the eye and can therefore be used as an objective index of the discomfort induced. The results compare favourably with subjective assessment.