Ocular tremor

Ocular microtremor (OMT) is a constant, physiological, high frequency (peak 80 Hz), low amplitude (estimated circa 150-2500 nm (1)) eye tremor. Ocular microtremor (OMT) is a constant, physiological, high frequency (peak 80 Hz), low amplitude (estimated circa 150-2500 nm (1)) eye tremor. It occurs in all normal people even when the eye is apparently still and is due to the constant activity of brainstem oculomotor units. In coma there is a loss of high frequency components of tremor and the extent of this reduction is related to the patient's prognosis (2). Ocular microtremor can potentially help in the difficult diagnosis of brainstem death, as well as monitoring patients while under anaesthesia (3). Abnormal OMT records are seen in neurological conditions such as Parkinson's disease and multiple sclerosis. The frequency spectrum also changes with age. The first description of what is now known as ocular microtremor was made in 1934 (4). More recent studies are less common for ocular microtremor than for other fixational eye movements. Some have suggested that the reason ocular microtremor studies are more rare may be because of the difficulty inherent in measuring microtremor. It is contentious whether ocular microtremor assists vision. Visual processes deteriorate rapidly in the absence of retinal image motion, with Stabilized Images. Some have suggested that tremor may not be a distinct eye movement at all.