thumb|Ocular microtremor tracing with burst sections underlined
Ocular tremor (ocular microtremor) is a constant, involuntary eye tremor of a low amplitude and high frequency. It is a type of fixational eye movement that occurs in all normal people, even when the eye appears still. The frequency of ocular microtremor has been found to range from 30 Hz to 103 Hz, and the amplitude is approximately four thousandths of a degree.
Cause
Human eyes are constantly moving, even if they appear to be focused on an object. Ocular tremor is the smallest of these movements, and it often overlaps with drift. It has also been suggested that ocular tremor is a result of the eye being balanced between opposing muscles.