Ocular tremor: Difference between revisions
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[[File:Tremblement oculaire.jpg|thumb|Ocular microtremor tracing with burst sections underlined]] |
[[File:Tremblement oculaire.jpg|thumb|Ocular microtremor tracing with burst sections underlined]] |
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'''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|fixational eye movement]] that occurs in all normal people, even when the eye appears still.<ref name=":1">{{Citation|last=Alexander|first=Robert G.|title=Fixational Eye Movements|date=2019|url=https://doi.org/10.1007/978-3-030-20085-5_3|work=Eye Movement Research: An Introduction to its Scientific Foundations and Applications|pages=73–115|editor-last=Klein|editor-first=Christoph|series=Studies in Neuroscience, Psychology and Behavioral Economics|place=Cham|publisher=Springer International Publishing|language=en|doi=10.1007/978-3-030-20085-5_3|isbn=978-3-030-20085-5|access-date=2021-11-06|last2=Martinez-Conde|first2=Susana|editor2-last=Ettinger|editor2-first=Ulrich}}</ref> 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.<ref name=":1" /><ref name=":2">{{Citation|last=Shakhnovich|first=A. R.|title=Fixation Movements of the Eyes|date=1977|url=http://link.springer.com/10.1007/978-1-4684-6964-6_2|work=The Brain and Regulation of Eye Movement|pages=23–66|place=Boston, MA|publisher=Springer US|language=en|doi=10.1007/978-1-4684-6964-6_2|isbn=978-1-4684-6966-0|access-date=2021-11-06}}</ref> |
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'''Ocular microtremor''' ('''OMT''') is a constant, physiological, high frequency (peak 80 Hz), low amplitude (estimated circa 150-2500 nm (1)) [[human eye|eye]] [[tremor]]. |
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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]].<ref>{{cite journal |last1=Bolger |first1=C |last2=Bojanic |first2=S |last3=Sheahan |first3=N |last4=Malone |first4=J |last5=Hutchinson |first5=M |last6=Coakley |first6=D |title=Ocular microtremor (OMT): a new neurophysiological approach to multiple sclerosis |journal=J Neurol Neurosurg Psychiatry |date=2000 |volume=68 |issue=5 |pages=639–42 |doi=10.1136/jnnp.68.5.639 |pmid=10766897 |pmc=1736931}}</ref> The frequency spectrum also changes with age.{{citation needed|date=December 2018}} |
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]].<ref>{{cite journal |last1=Bolger |first1=C |last2=Bojanic |first2=S |last3=Sheahan |first3=N |last4=Malone |first4=J |last5=Hutchinson |first5=M |last6=Coakley |first6=D |title=Ocular microtremor (OMT): a new neurophysiological approach to multiple sclerosis |journal=J Neurol Neurosurg Psychiatry |date=2000 |volume=68 |issue=5 |pages=639–42 |doi=10.1136/jnnp.68.5.639 |pmid=10766897 |pmc=1736931}}</ref> The frequency spectrum also changes with age.{{citation needed|date=December 2018}} |
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Revision as of 21:16, 5 December 2021
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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.[1] 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.[1][2]
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.[3] The frequency spectrum also changes with age.[citation needed]
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.[4] It is contentious whether ocular microtremor assists vision.[citation needed] Visual processes deteriorate rapidly in the absence of retinal image motion, with Stabilized Images.[5]
Some have suggested that tremor may not be a distinct eye movement at all.[6]
See also
References
1. Sheahan, N. F., Coakley, D., et al. (1993). "Ocular microtremor measurement system: design and performance." Med Biol Eng Comput 31(3): 205–12.
2. Coakley, D. and J. G. Thomas (1977). "The ocular microtremor record and the prognosis of the unconscious patient." Lancet 1(8010): 512–5.
3. Bojanic, S., T. Simpson, et al. (2001). "Ocular microtremor: a tool for measuring depth of anaesthesia?" Br J Anaesth 86(4): 519–22.
4. Adler, F. H. M., Fliegelman, Maurice (AB) (1934). "Influence of Fixation on the Visual Acuity." Archives of Ophthalmology 12: 475–483.
- ^ a b Alexander, Robert G.; Martinez-Conde, Susana (2019), Klein, Christoph; Ettinger, Ulrich (eds.), "Fixational Eye Movements", Eye Movement Research: An Introduction to its Scientific Foundations and Applications, Studies in Neuroscience, Psychology and Behavioral Economics, Cham: Springer International Publishing, pp. 73–115, doi:10.1007/978-3-030-20085-5_3, ISBN 978-3-030-20085-5, retrieved 2021-11-06
- ^ Shakhnovich, A. R. (1977), "Fixation Movements of the Eyes", The Brain and Regulation of Eye Movement, Boston, MA: Springer US, pp. 23–66, doi:10.1007/978-1-4684-6964-6_2, ISBN 978-1-4684-6966-0, retrieved 2021-11-06
- ^ Bolger, C; Bojanic, S; Sheahan, N; Malone, J; Hutchinson, M; Coakley, D (2000). "Ocular microtremor (OMT): a new neurophysiological approach to multiple sclerosis". J Neurol Neurosurg Psychiatry. 68 (5): 639–42. doi:10.1136/jnnp.68.5.639. PMC 1736931. PMID 10766897.
- ^ Alexander, Robert; Macknik, Stephen; Martinez-Conde, Susana (2018). "Microsaccade Characteristics in Neurological and Ophthalmic Disease". Frontiers in Neurology. 9 (144): 144. doi:10.3389/fneur.2018.00144. PMC 5859063. PMID 29593642.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ Rucci, Michele; Desbordes, Gaëlle (2003). "Contributions of fixational eye movements to the discrimination of briefly presented stimuli". Journal of Vision. 3 (11): 852–64. doi:10.1167/3.11.18. PMID 14765967.
- ^ Stevenson, Scott B.; Roorda, Austin; Kumar, Girish (2010). "Eye tracking with the adaptive optics scanning laser ophthalmoscope". Proceedings of the 2010 Symposium on Eye-Tracking Research & Applications - ETRA '10. p. 195. doi:10.1145/1743666.1743714. ISBN 9781605589947.
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