In the field of eye tracking, greater accuracy or resolution in monitoring movement of the eye can be gained by digitizing the eye, and tracking the movement of a landmark with fixed size and a fixed location relative to the eyes local coordinate system. The edge of the iris can be used as such a fixed landmark. Through the location and or establishment of at least a portion of the outer edge of the iris and/or an iris center point, both large and small scale eye movements, including but not limited to micro-tremors, can be traced with a higher degree of accuracy. This will aid in the diagnosis of diseases, assessing state of consciousness, and defining brainstem death.
