Ocular microtremor measurement using laser-speckle metrology

Kenny, Emer; Coakley, Davis; Boyle, Gerry

doi:10.1117/1.jbo.18.1.016010

Cited by 7 publications

(8 citation statements)

References 25 publications

(32 reference statements)

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“…Speculativeness notwithstanding, we believe that the proposal of testable hypotheses is a positive way to motivate the publicization of data and structure further empirical investigations in this area. Another high resolution non-contact FEM measurement method which can resolve tremor has recently been reported by Kenny et al (2013a,b), so data of sufficient resolution may soon become available from this group.…”

Section: Fixational Eye Movementsmentioning

confidence: 99%

Capture of fixation by rotational flow; a deterministic hypothesis regarding scaling and stochasticity in fixational eye movements

Wilkinson

Metta

2014

Front. Syst. Neurosci.

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Visual scan paths exhibit complex, stochastic dynamics. Even during visual fixation, the eye is in constant motion. Fixational drift and tremor are thought to reflect fluctuations in the persistent neural activity of neural integrators in the oculomotor brainstem, which integrate sequences of transient saccadic velocity signals into a short term memory of eye position. Despite intensive research and much progress, the precise mechanisms by which oculomotor posture is maintained remain elusive. Drift exhibits a stochastic statistical profile which has been modeled using random walk formalisms. Tremor is widely dismissed as noise. Here we focus on the dynamical profile of fixational tremor, and argue that tremor may be a signal which usefully reflects the workings of oculomotor postural control. We identify signatures reminiscent of a certain flavor of transient neurodynamics; toric traveling waves which rotate around a central phase singularity. Spiral waves play an organizational role in dynamical systems at many scales throughout nature, though their potential functional role in brain activity remains a matter of educated speculation. Spiral waves have a repertoire of functionally interesting dynamical properties, including persistence, which suggest that they could in theory contribute to persistent neural activity in the oculomotor postural control system. Whilst speculative, the singularity hypothesis of oculomotor postural control implies testable predictions, and could provide the beginnings of an integrated dynamical framework for eye movements across scales.

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Section: Fixational Eye Movementsmentioning

confidence: 99%

Capture of fixation by rotational flow; a deterministic hypothesis regarding scaling and stochasticity in fixational eye movements

Wilkinson

Metta

2014

Front. Syst. Neurosci.

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“…32 Volume scattering occurs when light penetrates a surface and undergoes multiple scattering before emerging from the surface. 18 A single scattering surface is a simplified model of what is expected in vivo. Speckle patterns from a material into which light penetrates are composed of different sized speckle: (1) large speckles originating from light scattered from the surface and (2) smaller speckles produced by light emerging from the inner volume of the material.…”

Section: Volume Scatteringmentioning

confidence: 99%

“…An OMT simulator device 18 with an inanimate cardboard surface was used so that the level of stability achievable with biospeckle could be compared to that of a nonbiological reference. The procedure above was repeated using the OMT simulator.…”

Section: In-vitro Comparisonmentioning

confidence: 99%

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Biospeckle in the human sclera and impact on laser speckle correlation measurement of eye tremor

2013

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Ocular microtremor (OMT) is an involuntary fixational eye movement. We identify the implications of biospeckle for a noninvasive, laser speckle correlation technique to measure OMT. Biospeckle from the in-vivo eye is characterized and, using the resulting characteristics, a mathematical model to describe the biospeckle from the eye is designed and tested. Through in-vivo measurements, biospeckle is shown to disrupt the temporal stability of the speckle images over time. However, provided each speckle image is cross correlated with the previous image within a sufficiently short time, the stability of speckle images captured from the eye is shown to be adequate to measure OMT-like displacements.

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“…However, similar laser safety considerations as in the case of the speckle interferometric technique must be adhered to when using speckle imaging while attempting to measure OMT. 7,33,34 In the 1950s, researchers in the Kodak Eastman company measured both the amplitude and frequency of OMT (Ref. 35) in one direction.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous drift, microsaccades, and ocular microtremor measurement from a single noncontact far-field optical sensor

2015

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We report on the combined far-field measurement of the three involuntary eye movements, drift, microsaccades, and ocular microtremor (OMT), using a noncontact far-field optical method. We review the significance of the smallest and least measured, and thus least understood, of the three, OMT. Using modern digital imaging techniques, we perform detailed analysis, present experimental results, and examine the extracted parameters using a noncontact far-field sensor. For the first time, in vivo noncontact measurements of all fixational in-plane movements of the human eye are reported, which simultaneously provide both the horizontal (left-right) and vertical (up-down) displacement results.

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Ocular microtremor measurement using laser-speckle metrology

Cited by 7 publications

References 25 publications

Capture of fixation by rotational flow; a deterministic hypothesis regarding scaling and stochasticity in fixational eye movements

Capture of fixation by rotational flow; a deterministic hypothesis regarding scaling and stochasticity in fixational eye movements

Biospeckle in the human sclera and impact on laser speckle correlation measurement of eye tremor

Simultaneous drift, microsaccades, and ocular microtremor measurement from a single noncontact far-field optical sensor

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