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

Kenny, Emer; Coakley, Davis; Boyle, Gerry

doi:10.1117/1.jbo.18.9.097009

Cited by 6 publications

(2 citation statements)

References 30 publications

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“…Furthermore, when recording speckle from a living object, a form of time-varying speckle referred to as 'biospeckle' is expected. However, it has been shown that when recorded at a frame rate of 500 Hz, despite of the presence of biospeckle, the speckle captured from the eye sclera is reasonably stable between successive image frames and biospeckle alone has no systematic influence on the angular displacement measurement from the sclera (Kenny et al 2013a).…”

Section: Laser Speckle Correlation Metrologymentioning

confidence: 99%

Non-contactin vivomeasurement of ocular microtremor using laser speckle correlation metrology

Kenny¹,

Coakley²,

Boyle³

2014

Physiol. Meas.

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Ocular microtremor (OMT) is a small involuntary eye movement present in all subjects. In this paper we present the results of in vivo OMT measurement using a novel non-contact laser speckle technique. OMT signals have not previously been measured from the sclera using this laser speckle correlation technique. To verify the system's ability to record eye movements, it is first tested using a large angle eye rotation. Next, the system is tested with a group of 20 subjects and OMT parameters are extracted. The results of OMT measurements gave a mean frequency of 78 ± 3.86 Hz and peak-to-peak amplitude of 21.42 ± 7.01 µrad, these values are consistent with known values from eye-contacting methods.

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Section: Laser Speckle Correlation Metrologymentioning

confidence: 99%

Non-contactin vivomeasurement of ocular microtremor using laser speckle correlation metrology

Kenny¹,

Coakley²,

Boyle³

2014

Physiol. Meas.

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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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Advances in Speckle Metrology

Joenathan

Sirohi

Bernal

2015

The Optics Encyclopedia

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The field of speckle metrology has seen a surge in development in the past 10 years owing to advancements in digital cameras and computing power. For instance, a variety of digital speckle correlation (DSC) processes can now be performed in almost real time and therefore speckle techniques has found applications in nondestructive testing (NDT), biology, and medicine. New techniques in terms of optical arrangements and in extracting phase data have been introduced for measuring out‐of‐plane and in‐plane motions in digital speckle interferometry (DSPI) and digital speckle shear interferometry (DSSPI). DSC, DSPI, and DSSPI have also been combined to extend the range of measurements. In addition, quantitative analysis in speckle interferometry has seen a plethora of new software developments for conducting real‐time, accurate, complicated, fast, and repeatable measurements with ease. In addition, different methods to process speckle fringes have made analysis equivalent to that of classical interferometry, yet can be applied to all types of real‐world specimen.

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

Cited by 6 publications

References 30 publications

Non-contactin vivomeasurement of ocular microtremor using laser speckle correlation metrology

Non-contactin vivomeasurement of ocular microtremor using laser speckle correlation metrology

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

Advances in Speckle Metrology

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