Interferometry for ocular microtremor measurement.

The eyes of all normal subjects undergo a continuous, low-amplitude, high-frequency tremor called ocular microtremor (OMT). A number of potential clinical applications of OMT have been identified, including the prediction of outcome in coma. To date, OMT has been investigated primarily with an eye-contacting piezoelectric probe. We describe a laser-based, noncontacting, interferometric technique for the measurement of OMT. The technique employs an in-plane-sensitive, phase-modulating speckle interferometer to detect the movement of the sclera, or white of the eye.