Abstract

The eyes of all normal subjects undergo a continuous, low-amplitude, high-frequency tremor called ocular microtremor (OMT). A number of potential clinical applications of OMT have been identified, including the prediction of outcome in coma. To date, OMT has been investigated primarily with an eye-contacting piezoelectric probe. We describe a laser-based, noncontacting, interferometric technique for the measurement of OMT. The technique employs an in-plane-sensitive, phase-modulating speckle interferometer to detect the movement of the sclera, or white of the eye.

© 2001 Optical Society of America

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  1. C. Bolger, “Ocular microtremor, reliability of measurement, physiological variation and neurogenic origin,” Ph.D. dissertation (Trinity College, Dublin, 1994).
  2. M. Eizenman, R. C. Frecker, P. E. Hallett, “Precise non-contacting measurement of eye movements using the corneal reflex,” Vision Res. 24, 167–174 (1984).
    [CrossRef] [PubMed]
  3. N. Sheahan, “OMT measurement technique and biophysical analysis,” Ph.D. dissertation (Trinity College, Dublin, 1991).
  4. C. Bolger, S. Bojanic, N. F. Sheahan, D. Coakley, J. F. Malone, “Dominant frequency content of ocular microtremor from normal subjects,” Vision Res. 39, 1911–1915 (1999).
    [CrossRef] [PubMed]
  5. D. Coakley, Minute Eye Movement And Brainstem Function (CRC, Boca Raton, Fla., 1983).
  6. D. Coakley, J. G. Thomas, “The ocular microtremor record and the prognosis of the unconscious patient,” Lancet 5, 512–515 (1977).
    [CrossRef]
  7. D. Coakley, J. G. Thomas, “The ocular microtremor record as a potential procedure for establishing brain death,” J. Neurol. Sci. 31, 199–205 (1977).
    [CrossRef] [PubMed]
  8. D. Coakley, R. Williams, J. Morris, “Minute eye movment during sleep,” Electroencephalogr. Clin. Neurophysiol. 47, 126–131 (1979).
    [CrossRef] [PubMed]
  9. C. Bolger, S. Bojanic, N. Sheahan, J. Malone, M. Hutchinson, D. Coakley, “Ocular microtremor (OMT): a new neurophysiological approach to multiple sclerosis,” J. Neurol. Neurosurg. Psychiatry 68, 639–642 (2000).
    [CrossRef] [PubMed]
  10. C. Bolger, S. Bojanic, N. F. Sheahan, D. Coakley, J. F. Malone, “Ocular microtremor in patients with idiopathic Parkinson’s disease,” J. Neurol. Neurosurg. Psychiatry 66, 528–531.
  11. N. F. Sheahan, D. Coakley, F. Hegarty, C. Bolger, J. Malone, “Ocular microtremor measurement system: design and performance,” Med. Biol. Eng. Comput. 31, 205–212 (1993).
    [CrossRef] [PubMed]
  12. N. F. Sheahan, D. Coakley, C. Bolger, D. O’Neill, G. Fry, J. Phillips, J. F. Malone, “Sources of variance in ocular microtremor,” Physiol. Meas. 15, 101–106 (1994).
    [CrossRef] [PubMed]
  13. H. D. Crane, C. M. Steele, “Generation-V dual Purkinje-image tracker,” Appl. Opt. 24, 527–704 (1985).
    [CrossRef]
  14. J. P. H. Reulen, J. T. Marcus, D. Koops, F. R. de Vries, G. Tiesenga, K. Boshuizen, J. E. Bos, “Precise recording of eye movement by the IRIS technique Pt. I,” Med. Biol. Eng. Comput. 26, 20–26 (1988).
    [CrossRef] [PubMed]
  15. R. W. Ditchburn, B. L. Ginsborg, “Involuntary eye movements during fixation,” J. Physiol. 119, 1–17 (1952).
  16. L. A. Riggs, J. C. Armington, F. Ratliff, “Motions of the retinal image during fixation,” J. Opt. Soc. Am. 44, 315–321 (1954).
    [CrossRef] [PubMed]
  17. F. Ratliff, L. A. Riggs, “Involuntary motion of the eye during fixation,” J. Exp. Pyschol. 40, 687–701 (1950).
    [CrossRef]
  18. R. H. S. Carpenter, Movements of the Eyes (Pion, London, 1988).
  19. S. Ul’yanov, V. Ryabukho, “Speckle interferometry for biotissue vibration measurement,” Opt. Eng. 33, 908–914 (1994).
    [CrossRef]
  20. I. A. Popov, L. M. Vesolov, “Mechanical vibration spectrum analysis by means of a speckle method,” Opt. Commun. 105, 167–170 (1994).
    [CrossRef]
  21. R. Dandliker, J.-F. Willemin, “Measuring microvibrations by heterodyne speckle interferometry,” J. Opt. Soc. Am. 6, 165–167 (1981).
  22. J. A. Leendertz, “Interferometric displacement measurement on scattering surfaces using the speckle effect,” J. Phys. E. 3, 214–218 (1970).
    [CrossRef]
  23. T. Suzuki, O. Sasaki, S. Takayama, T. Maruyama, “Real time displacement measurement using synchronous detection in a sinusoidal phase modulating interferometer,” Opt. Eng. 32, 1033–1037 (1993).
    [CrossRef]
  24. T. Suzuki, O. Sasaki, K. Higuchi, T. Maruyama, “Real-time displacement measurement in sinusoidal phase modulating interferometry,” Appl. Opt. 28, 5270–5274 (1989).
    [CrossRef] [PubMed]
  25. O. Sasaki, K. Takahasi, “Sinusoidal phase modulating interferometer using optical fibers for displacement measurements,” Appl. Opt. 27, 4139–4142 (1988).
    [CrossRef] [PubMed]
  26. G. Boyle, “Ocular microtremor, non-contacting measurement and biophysical analysis,” Ph.D. dissertation (Trinity College, Dublin, 1998).
  27. IEC International Standard 825–1 (International Electrotechnical Commission, Geneva, Switzerland, 1993).
  28. J. D. Briers, “Speckle fluctuations and biomedical optics: implications and applications,” Opt. Eng. 32, 277–283. (1993).
    [CrossRef]

2000

C. Bolger, S. Bojanic, N. Sheahan, J. Malone, M. Hutchinson, D. Coakley, “Ocular microtremor (OMT): a new neurophysiological approach to multiple sclerosis,” J. Neurol. Neurosurg. Psychiatry 68, 639–642 (2000).
[CrossRef] [PubMed]

1999

C. Bolger, S. Bojanic, N. F. Sheahan, D. Coakley, J. F. Malone, “Dominant frequency content of ocular microtremor from normal subjects,” Vision Res. 39, 1911–1915 (1999).
[CrossRef] [PubMed]

1994

N. F. Sheahan, D. Coakley, C. Bolger, D. O’Neill, G. Fry, J. Phillips, J. F. Malone, “Sources of variance in ocular microtremor,” Physiol. Meas. 15, 101–106 (1994).
[CrossRef] [PubMed]

S. Ul’yanov, V. Ryabukho, “Speckle interferometry for biotissue vibration measurement,” Opt. Eng. 33, 908–914 (1994).
[CrossRef]

I. A. Popov, L. M. Vesolov, “Mechanical vibration spectrum analysis by means of a speckle method,” Opt. Commun. 105, 167–170 (1994).
[CrossRef]

1993

N. F. Sheahan, D. Coakley, F. Hegarty, C. Bolger, J. Malone, “Ocular microtremor measurement system: design and performance,” Med. Biol. Eng. Comput. 31, 205–212 (1993).
[CrossRef] [PubMed]

T. Suzuki, O. Sasaki, S. Takayama, T. Maruyama, “Real time displacement measurement using synchronous detection in a sinusoidal phase modulating interferometer,” Opt. Eng. 32, 1033–1037 (1993).
[CrossRef]

J. D. Briers, “Speckle fluctuations and biomedical optics: implications and applications,” Opt. Eng. 32, 277–283. (1993).
[CrossRef]

1989

1988

O. Sasaki, K. Takahasi, “Sinusoidal phase modulating interferometer using optical fibers for displacement measurements,” Appl. Opt. 27, 4139–4142 (1988).
[CrossRef] [PubMed]

J. P. H. Reulen, J. T. Marcus, D. Koops, F. R. de Vries, G. Tiesenga, K. Boshuizen, J. E. Bos, “Precise recording of eye movement by the IRIS technique Pt. I,” Med. Biol. Eng. Comput. 26, 20–26 (1988).
[CrossRef] [PubMed]

1985

1984

M. Eizenman, R. C. Frecker, P. E. Hallett, “Precise non-contacting measurement of eye movements using the corneal reflex,” Vision Res. 24, 167–174 (1984).
[CrossRef] [PubMed]

1981

R. Dandliker, J.-F. Willemin, “Measuring microvibrations by heterodyne speckle interferometry,” J. Opt. Soc. Am. 6, 165–167 (1981).

1979

D. Coakley, R. Williams, J. Morris, “Minute eye movment during sleep,” Electroencephalogr. Clin. Neurophysiol. 47, 126–131 (1979).
[CrossRef] [PubMed]

1977

D. Coakley, J. G. Thomas, “The ocular microtremor record and the prognosis of the unconscious patient,” Lancet 5, 512–515 (1977).
[CrossRef]

D. Coakley, J. G. Thomas, “The ocular microtremor record as a potential procedure for establishing brain death,” J. Neurol. Sci. 31, 199–205 (1977).
[CrossRef] [PubMed]

1970

J. A. Leendertz, “Interferometric displacement measurement on scattering surfaces using the speckle effect,” J. Phys. E. 3, 214–218 (1970).
[CrossRef]

1954

1952

R. W. Ditchburn, B. L. Ginsborg, “Involuntary eye movements during fixation,” J. Physiol. 119, 1–17 (1952).

1950

F. Ratliff, L. A. Riggs, “Involuntary motion of the eye during fixation,” J. Exp. Pyschol. 40, 687–701 (1950).
[CrossRef]

Armington, J. C.

Bojanic, S.

C. Bolger, S. Bojanic, N. Sheahan, J. Malone, M. Hutchinson, D. Coakley, “Ocular microtremor (OMT): a new neurophysiological approach to multiple sclerosis,” J. Neurol. Neurosurg. Psychiatry 68, 639–642 (2000).
[CrossRef] [PubMed]

C. Bolger, S. Bojanic, N. F. Sheahan, D. Coakley, J. F. Malone, “Dominant frequency content of ocular microtremor from normal subjects,” Vision Res. 39, 1911–1915 (1999).
[CrossRef] [PubMed]

C. Bolger, S. Bojanic, N. F. Sheahan, D. Coakley, J. F. Malone, “Ocular microtremor in patients with idiopathic Parkinson’s disease,” J. Neurol. Neurosurg. Psychiatry 66, 528–531.

Bolger, C.

C. Bolger, S. Bojanic, N. Sheahan, J. Malone, M. Hutchinson, D. Coakley, “Ocular microtremor (OMT): a new neurophysiological approach to multiple sclerosis,” J. Neurol. Neurosurg. Psychiatry 68, 639–642 (2000).
[CrossRef] [PubMed]

C. Bolger, S. Bojanic, N. F. Sheahan, D. Coakley, J. F. Malone, “Dominant frequency content of ocular microtremor from normal subjects,” Vision Res. 39, 1911–1915 (1999).
[CrossRef] [PubMed]

N. F. Sheahan, D. Coakley, C. Bolger, D. O’Neill, G. Fry, J. Phillips, J. F. Malone, “Sources of variance in ocular microtremor,” Physiol. Meas. 15, 101–106 (1994).
[CrossRef] [PubMed]

N. F. Sheahan, D. Coakley, F. Hegarty, C. Bolger, J. Malone, “Ocular microtremor measurement system: design and performance,” Med. Biol. Eng. Comput. 31, 205–212 (1993).
[CrossRef] [PubMed]

C. Bolger, S. Bojanic, N. F. Sheahan, D. Coakley, J. F. Malone, “Ocular microtremor in patients with idiopathic Parkinson’s disease,” J. Neurol. Neurosurg. Psychiatry 66, 528–531.

C. Bolger, “Ocular microtremor, reliability of measurement, physiological variation and neurogenic origin,” Ph.D. dissertation (Trinity College, Dublin, 1994).

Bos, J. E.

J. P. H. Reulen, J. T. Marcus, D. Koops, F. R. de Vries, G. Tiesenga, K. Boshuizen, J. E. Bos, “Precise recording of eye movement by the IRIS technique Pt. I,” Med. Biol. Eng. Comput. 26, 20–26 (1988).
[CrossRef] [PubMed]

Boshuizen, K.

J. P. H. Reulen, J. T. Marcus, D. Koops, F. R. de Vries, G. Tiesenga, K. Boshuizen, J. E. Bos, “Precise recording of eye movement by the IRIS technique Pt. I,” Med. Biol. Eng. Comput. 26, 20–26 (1988).
[CrossRef] [PubMed]

Boyle, G.

G. Boyle, “Ocular microtremor, non-contacting measurement and biophysical analysis,” Ph.D. dissertation (Trinity College, Dublin, 1998).

Briers, J. D.

J. D. Briers, “Speckle fluctuations and biomedical optics: implications and applications,” Opt. Eng. 32, 277–283. (1993).
[CrossRef]

Carpenter, R. H. S.

R. H. S. Carpenter, Movements of the Eyes (Pion, London, 1988).

Coakley, D.

C. Bolger, S. Bojanic, N. Sheahan, J. Malone, M. Hutchinson, D. Coakley, “Ocular microtremor (OMT): a new neurophysiological approach to multiple sclerosis,” J. Neurol. Neurosurg. Psychiatry 68, 639–642 (2000).
[CrossRef] [PubMed]

C. Bolger, S. Bojanic, N. F. Sheahan, D. Coakley, J. F. Malone, “Dominant frequency content of ocular microtremor from normal subjects,” Vision Res. 39, 1911–1915 (1999).
[CrossRef] [PubMed]

N. F. Sheahan, D. Coakley, C. Bolger, D. O’Neill, G. Fry, J. Phillips, J. F. Malone, “Sources of variance in ocular microtremor,” Physiol. Meas. 15, 101–106 (1994).
[CrossRef] [PubMed]

N. F. Sheahan, D. Coakley, F. Hegarty, C. Bolger, J. Malone, “Ocular microtremor measurement system: design and performance,” Med. Biol. Eng. Comput. 31, 205–212 (1993).
[CrossRef] [PubMed]

D. Coakley, R. Williams, J. Morris, “Minute eye movment during sleep,” Electroencephalogr. Clin. Neurophysiol. 47, 126–131 (1979).
[CrossRef] [PubMed]

D. Coakley, J. G. Thomas, “The ocular microtremor record as a potential procedure for establishing brain death,” J. Neurol. Sci. 31, 199–205 (1977).
[CrossRef] [PubMed]

D. Coakley, J. G. Thomas, “The ocular microtremor record and the prognosis of the unconscious patient,” Lancet 5, 512–515 (1977).
[CrossRef]

D. Coakley, Minute Eye Movement And Brainstem Function (CRC, Boca Raton, Fla., 1983).

C. Bolger, S. Bojanic, N. F. Sheahan, D. Coakley, J. F. Malone, “Ocular microtremor in patients with idiopathic Parkinson’s disease,” J. Neurol. Neurosurg. Psychiatry 66, 528–531.

Crane, H. D.

Dandliker, R.

R. Dandliker, J.-F. Willemin, “Measuring microvibrations by heterodyne speckle interferometry,” J. Opt. Soc. Am. 6, 165–167 (1981).

de Vries, F. R.

J. P. H. Reulen, J. T. Marcus, D. Koops, F. R. de Vries, G. Tiesenga, K. Boshuizen, J. E. Bos, “Precise recording of eye movement by the IRIS technique Pt. I,” Med. Biol. Eng. Comput. 26, 20–26 (1988).
[CrossRef] [PubMed]

Ditchburn, R. W.

R. W. Ditchburn, B. L. Ginsborg, “Involuntary eye movements during fixation,” J. Physiol. 119, 1–17 (1952).

Eizenman, M.

M. Eizenman, R. C. Frecker, P. E. Hallett, “Precise non-contacting measurement of eye movements using the corneal reflex,” Vision Res. 24, 167–174 (1984).
[CrossRef] [PubMed]

Frecker, R. C.

M. Eizenman, R. C. Frecker, P. E. Hallett, “Precise non-contacting measurement of eye movements using the corneal reflex,” Vision Res. 24, 167–174 (1984).
[CrossRef] [PubMed]

Fry, G.

N. F. Sheahan, D. Coakley, C. Bolger, D. O’Neill, G. Fry, J. Phillips, J. F. Malone, “Sources of variance in ocular microtremor,” Physiol. Meas. 15, 101–106 (1994).
[CrossRef] [PubMed]

Ginsborg, B. L.

R. W. Ditchburn, B. L. Ginsborg, “Involuntary eye movements during fixation,” J. Physiol. 119, 1–17 (1952).

Hallett, P. E.

M. Eizenman, R. C. Frecker, P. E. Hallett, “Precise non-contacting measurement of eye movements using the corneal reflex,” Vision Res. 24, 167–174 (1984).
[CrossRef] [PubMed]

Hegarty, F.

N. F. Sheahan, D. Coakley, F. Hegarty, C. Bolger, J. Malone, “Ocular microtremor measurement system: design and performance,” Med. Biol. Eng. Comput. 31, 205–212 (1993).
[CrossRef] [PubMed]

Higuchi, K.

Hutchinson, M.

C. Bolger, S. Bojanic, N. Sheahan, J. Malone, M. Hutchinson, D. Coakley, “Ocular microtremor (OMT): a new neurophysiological approach to multiple sclerosis,” J. Neurol. Neurosurg. Psychiatry 68, 639–642 (2000).
[CrossRef] [PubMed]

Koops, D.

J. P. H. Reulen, J. T. Marcus, D. Koops, F. R. de Vries, G. Tiesenga, K. Boshuizen, J. E. Bos, “Precise recording of eye movement by the IRIS technique Pt. I,” Med. Biol. Eng. Comput. 26, 20–26 (1988).
[CrossRef] [PubMed]

Leendertz, J. A.

J. A. Leendertz, “Interferometric displacement measurement on scattering surfaces using the speckle effect,” J. Phys. E. 3, 214–218 (1970).
[CrossRef]

Malone, J.

C. Bolger, S. Bojanic, N. Sheahan, J. Malone, M. Hutchinson, D. Coakley, “Ocular microtremor (OMT): a new neurophysiological approach to multiple sclerosis,” J. Neurol. Neurosurg. Psychiatry 68, 639–642 (2000).
[CrossRef] [PubMed]

N. F. Sheahan, D. Coakley, F. Hegarty, C. Bolger, J. Malone, “Ocular microtremor measurement system: design and performance,” Med. Biol. Eng. Comput. 31, 205–212 (1993).
[CrossRef] [PubMed]

Malone, J. F.

C. Bolger, S. Bojanic, N. F. Sheahan, D. Coakley, J. F. Malone, “Dominant frequency content of ocular microtremor from normal subjects,” Vision Res. 39, 1911–1915 (1999).
[CrossRef] [PubMed]

N. F. Sheahan, D. Coakley, C. Bolger, D. O’Neill, G. Fry, J. Phillips, J. F. Malone, “Sources of variance in ocular microtremor,” Physiol. Meas. 15, 101–106 (1994).
[CrossRef] [PubMed]

C. Bolger, S. Bojanic, N. F. Sheahan, D. Coakley, J. F. Malone, “Ocular microtremor in patients with idiopathic Parkinson’s disease,” J. Neurol. Neurosurg. Psychiatry 66, 528–531.

Marcus, J. T.

J. P. H. Reulen, J. T. Marcus, D. Koops, F. R. de Vries, G. Tiesenga, K. Boshuizen, J. E. Bos, “Precise recording of eye movement by the IRIS technique Pt. I,” Med. Biol. Eng. Comput. 26, 20–26 (1988).
[CrossRef] [PubMed]

Maruyama, T.

T. Suzuki, O. Sasaki, S. Takayama, T. Maruyama, “Real time displacement measurement using synchronous detection in a sinusoidal phase modulating interferometer,” Opt. Eng. 32, 1033–1037 (1993).
[CrossRef]

T. Suzuki, O. Sasaki, K. Higuchi, T. Maruyama, “Real-time displacement measurement in sinusoidal phase modulating interferometry,” Appl. Opt. 28, 5270–5274 (1989).
[CrossRef] [PubMed]

Morris, J.

D. Coakley, R. Williams, J. Morris, “Minute eye movment during sleep,” Electroencephalogr. Clin. Neurophysiol. 47, 126–131 (1979).
[CrossRef] [PubMed]

O’Neill, D.

N. F. Sheahan, D. Coakley, C. Bolger, D. O’Neill, G. Fry, J. Phillips, J. F. Malone, “Sources of variance in ocular microtremor,” Physiol. Meas. 15, 101–106 (1994).
[CrossRef] [PubMed]

Phillips, J.

N. F. Sheahan, D. Coakley, C. Bolger, D. O’Neill, G. Fry, J. Phillips, J. F. Malone, “Sources of variance in ocular microtremor,” Physiol. Meas. 15, 101–106 (1994).
[CrossRef] [PubMed]

Popov, I. A.

I. A. Popov, L. M. Vesolov, “Mechanical vibration spectrum analysis by means of a speckle method,” Opt. Commun. 105, 167–170 (1994).
[CrossRef]

Ratliff, F.

L. A. Riggs, J. C. Armington, F. Ratliff, “Motions of the retinal image during fixation,” J. Opt. Soc. Am. 44, 315–321 (1954).
[CrossRef] [PubMed]

F. Ratliff, L. A. Riggs, “Involuntary motion of the eye during fixation,” J. Exp. Pyschol. 40, 687–701 (1950).
[CrossRef]

Reulen, J. P. H.

J. P. H. Reulen, J. T. Marcus, D. Koops, F. R. de Vries, G. Tiesenga, K. Boshuizen, J. E. Bos, “Precise recording of eye movement by the IRIS technique Pt. I,” Med. Biol. Eng. Comput. 26, 20–26 (1988).
[CrossRef] [PubMed]

Riggs, L. A.

L. A. Riggs, J. C. Armington, F. Ratliff, “Motions of the retinal image during fixation,” J. Opt. Soc. Am. 44, 315–321 (1954).
[CrossRef] [PubMed]

F. Ratliff, L. A. Riggs, “Involuntary motion of the eye during fixation,” J. Exp. Pyschol. 40, 687–701 (1950).
[CrossRef]

Ryabukho, V.

S. Ul’yanov, V. Ryabukho, “Speckle interferometry for biotissue vibration measurement,” Opt. Eng. 33, 908–914 (1994).
[CrossRef]

Sasaki, O.

Sheahan, N.

C. Bolger, S. Bojanic, N. Sheahan, J. Malone, M. Hutchinson, D. Coakley, “Ocular microtremor (OMT): a new neurophysiological approach to multiple sclerosis,” J. Neurol. Neurosurg. Psychiatry 68, 639–642 (2000).
[CrossRef] [PubMed]

N. Sheahan, “OMT measurement technique and biophysical analysis,” Ph.D. dissertation (Trinity College, Dublin, 1991).

Sheahan, N. F.

C. Bolger, S. Bojanic, N. F. Sheahan, D. Coakley, J. F. Malone, “Dominant frequency content of ocular microtremor from normal subjects,” Vision Res. 39, 1911–1915 (1999).
[CrossRef] [PubMed]

N. F. Sheahan, D. Coakley, C. Bolger, D. O’Neill, G. Fry, J. Phillips, J. F. Malone, “Sources of variance in ocular microtremor,” Physiol. Meas. 15, 101–106 (1994).
[CrossRef] [PubMed]

N. F. Sheahan, D. Coakley, F. Hegarty, C. Bolger, J. Malone, “Ocular microtremor measurement system: design and performance,” Med. Biol. Eng. Comput. 31, 205–212 (1993).
[CrossRef] [PubMed]

C. Bolger, S. Bojanic, N. F. Sheahan, D. Coakley, J. F. Malone, “Ocular microtremor in patients with idiopathic Parkinson’s disease,” J. Neurol. Neurosurg. Psychiatry 66, 528–531.

Steele, C. M.

Suzuki, T.

T. Suzuki, O. Sasaki, S. Takayama, T. Maruyama, “Real time displacement measurement using synchronous detection in a sinusoidal phase modulating interferometer,” Opt. Eng. 32, 1033–1037 (1993).
[CrossRef]

T. Suzuki, O. Sasaki, K. Higuchi, T. Maruyama, “Real-time displacement measurement in sinusoidal phase modulating interferometry,” Appl. Opt. 28, 5270–5274 (1989).
[CrossRef] [PubMed]

Takahasi, K.

Takayama, S.

T. Suzuki, O. Sasaki, S. Takayama, T. Maruyama, “Real time displacement measurement using synchronous detection in a sinusoidal phase modulating interferometer,” Opt. Eng. 32, 1033–1037 (1993).
[CrossRef]

Thomas, J. G.

D. Coakley, J. G. Thomas, “The ocular microtremor record and the prognosis of the unconscious patient,” Lancet 5, 512–515 (1977).
[CrossRef]

D. Coakley, J. G. Thomas, “The ocular microtremor record as a potential procedure for establishing brain death,” J. Neurol. Sci. 31, 199–205 (1977).
[CrossRef] [PubMed]

Tiesenga, G.

J. P. H. Reulen, J. T. Marcus, D. Koops, F. R. de Vries, G. Tiesenga, K. Boshuizen, J. E. Bos, “Precise recording of eye movement by the IRIS technique Pt. I,” Med. Biol. Eng. Comput. 26, 20–26 (1988).
[CrossRef] [PubMed]

Ul’yanov, S.

S. Ul’yanov, V. Ryabukho, “Speckle interferometry for biotissue vibration measurement,” Opt. Eng. 33, 908–914 (1994).
[CrossRef]

Vesolov, L. M.

I. A. Popov, L. M. Vesolov, “Mechanical vibration spectrum analysis by means of a speckle method,” Opt. Commun. 105, 167–170 (1994).
[CrossRef]

Willemin, J.-F.

R. Dandliker, J.-F. Willemin, “Measuring microvibrations by heterodyne speckle interferometry,” J. Opt. Soc. Am. 6, 165–167 (1981).

Williams, R.

D. Coakley, R. Williams, J. Morris, “Minute eye movment during sleep,” Electroencephalogr. Clin. Neurophysiol. 47, 126–131 (1979).
[CrossRef] [PubMed]

Appl. Opt.

Electroencephalogr. Clin. Neurophysiol.

D. Coakley, R. Williams, J. Morris, “Minute eye movment during sleep,” Electroencephalogr. Clin. Neurophysiol. 47, 126–131 (1979).
[CrossRef] [PubMed]

J. Exp. Pyschol.

F. Ratliff, L. A. Riggs, “Involuntary motion of the eye during fixation,” J. Exp. Pyschol. 40, 687–701 (1950).
[CrossRef]

J. Neurol. Neurosurg. Psychiatry

C. Bolger, S. Bojanic, N. Sheahan, J. Malone, M. Hutchinson, D. Coakley, “Ocular microtremor (OMT): a new neurophysiological approach to multiple sclerosis,” J. Neurol. Neurosurg. Psychiatry 68, 639–642 (2000).
[CrossRef] [PubMed]

C. Bolger, S. Bojanic, N. F. Sheahan, D. Coakley, J. F. Malone, “Ocular microtremor in patients with idiopathic Parkinson’s disease,” J. Neurol. Neurosurg. Psychiatry 66, 528–531.

J. Neurol. Sci.

D. Coakley, J. G. Thomas, “The ocular microtremor record as a potential procedure for establishing brain death,” J. Neurol. Sci. 31, 199–205 (1977).
[CrossRef] [PubMed]

J. Opt. Soc. Am.

L. A. Riggs, J. C. Armington, F. Ratliff, “Motions of the retinal image during fixation,” J. Opt. Soc. Am. 44, 315–321 (1954).
[CrossRef] [PubMed]

R. Dandliker, J.-F. Willemin, “Measuring microvibrations by heterodyne speckle interferometry,” J. Opt. Soc. Am. 6, 165–167 (1981).

J. Phys. E.

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[CrossRef]

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Lancet

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[CrossRef]

Med. Biol. Eng. Comput.

J. P. H. Reulen, J. T. Marcus, D. Koops, F. R. de Vries, G. Tiesenga, K. Boshuizen, J. E. Bos, “Precise recording of eye movement by the IRIS technique Pt. I,” Med. Biol. Eng. Comput. 26, 20–26 (1988).
[CrossRef] [PubMed]

N. F. Sheahan, D. Coakley, F. Hegarty, C. Bolger, J. Malone, “Ocular microtremor measurement system: design and performance,” Med. Biol. Eng. Comput. 31, 205–212 (1993).
[CrossRef] [PubMed]

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[CrossRef]

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[CrossRef]

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[CrossRef]

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[CrossRef]

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Figures (10)

Fig. 1
Fig. 1

Alignment of the laser beams with the eye in the interferometer for OMT measurement. The principle of the interferometer operation is based on that of in-plane speckle interferometers.

Fig. 2
Fig. 2

Notional spectrum of the phase-modulated interference signal. Sine interference terms (shown shaded) appear as amplitude-modulated signals with carrier frequencies of odd multiples of the phase-modulating frequency ω c . Cosine terms (shown clear) appear as amplitude-modulated signals with carrier frequencies of even multiples of ω c . Demodulation of the signals with carriers ω c and 2ω c recovers two interference signals in phase quadrature.

Fig. 3
Fig. 3

Block diagram of the demodulation process.

Fig. 4
Fig. 4

Interferometer for OMT measurement as seen from above, aligned to measure OMT in the right eye (RE). The axis of the interferometer is orientated at 35° to the direction of gaze. With the point of incidence of the beams targeted midway between the border of the iris and the lateral canthus, the interferometer axis will be approximately collinear with a normal to the sclera. LE, left eye; FL1, FL2, filters; L1, focusing lens; BS, beam splitter; M1, phase-modulating mirror; PZ, piezoelectric element; M2, M3, fixed mirrors; L2, L3, collecting lenses; PD, photodiode.

Fig. 5
Fig. 5

In-quadrature interference signals s s (t) and s c (t) generated with the OMT simulator as target, and displacement d(t) of the simulator as reconstructed by software from s s (t) and s c (t). The simulator is set vibrating at 1 µm peak to peak at 80 Hz. The displacement d(t) has been digitally bandpass filtered between 20 and 150 Hz.

Fig. 6
Fig. 6

In-quadrature interference signals s s (t) and s c (t) generated with a section of bovine sclera as target, and displacement d(t) of the bovine sclera as reconstructed by software from s s (t) and s c (t). The simulator is set vibrating at 1 µm peak to peak at 80 Hz. The displacement d(t) has been digitally bandpass filtered between 20 and 150 Hz.

Fig. 7
Fig. 7

Like Fig. 6, but in this case the interference signals shown have a noisy character that contaminated some of the data from the bovine sclera.

Fig. 8
Fig. 8

Upper trace, movement of a section of bovine sclera as measured by the interference technique. The section of sclera is mounted on the OMT simulator and driven by a signal on audiotape recorded from a normal human eye with the piezoelectric probe technique. Lower trace, actual movement of the bovine sclera as measured by the simulator piezoelectric sensing element.

Fig. 9
Fig. 9

Measured spectra of unfiltered eye movements with (i) no superimposed motion and (ii) a 1-µm peak-to-peak 140-Hz superimposed motion.

Fig. 10
Fig. 10

OMT trace recorded with interferometric technique.

Equations (12)

Equations on this page are rendered with MathJax. Learn more.

Δϕ=4π/λd sin θ.
st=U0 cosψ+ϕt
=U0 cosψ+4π/λdtsin θ,
st=U0 cos2π/λdt+z cos ωct+ψ0,
st=cos2π/λdtJ0z-2J2zcos 2ωct+2J4zcos 4ωct- -sin2π/λdt×2J1zcos ωct-2J3zcos 3ωct+ ,
sst=2J1zsin2π/λdt
sct=2J2zcos2π/λdt
B.W.=ωmax+2ωc,
cos2π/λdt.
ωmax=2πνmax/λ.
sct=cos2π/λdt,
sst=sin2π/λdt.

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