April 2011
Volume 52, Issue 14
Free
ARVO Annual Meeting Abstract  |   April 2011
The Light Induced Electromyogram (EMG): A Reflex Pathway Integrating the Melanopsin Retinal Ganglion Cell, Trigeminal Sensory Nucleus and Facial Nerve
Author Affiliations & Notes
  • Randy H. Kardon
    Ophthalmology and Visual Sciences, University of Iowa and Veterans Admin, Iowa City, Iowa
    Surgery/Research,
    Department of Veterans Affairs, Center for the Prevention and Treatment of Vision Loss, Iowa City, Iowa
  • Susan C. Anderson
    Ophthalmology and Visual Sciences, University of Iowa and Veterans Admin, Iowa City, Iowa
    Research,
    Department of Veterans Affairs, Center for the Prevention and Treatment of Vision Loss, Iowa City, Iowa
  • Jan Full
    Research,
    Department of Veterans Affairs, Center for the Prevention and Treatment of Vision Loss, Iowa City, Iowa
  • Pieter Poolman
    Ophthalmology and Visual Sciences, University of Iowa and Veterans Admin, Iowa City, Iowa
    Research,
    Department of Veterans Affairs, Center for the Prevention and Treatment of Vision Loss, Iowa City, Iowa
  • Footnotes
    Commercial Relationships  Randy H. Kardon, None; Susan C. Anderson, None; Jan Full, None; Pieter Poolman, None
  • Footnotes
    Support  Department of Veterans Affairs Rehabilitaton, Research and Development Division, Iowa City VA Center for the Prevention and Treatment of Vision Loss
Investigative Ophthalmology & Visual Science April 2011, Vol.52, 269. doi:
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      Randy H. Kardon, Susan C. Anderson, Jan Full, Pieter Poolman; The Light Induced Electromyogram (EMG): A Reflex Pathway Integrating the Melanopsin Retinal Ganglion Cell, Trigeminal Sensory Nucleus and Facial Nerve. Invest. Ophthalmol. Vis. Sci. 2011;52(14):269.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: : The Photo-Blink Reflex protects the eye after a bright flash of light (Mukuno et al 1983, Malin 1982, Yasahura et al 1982, Ozaki 1976). Melanopsin containing retinal ganglion cells may comprise the afferent arm of this reflex through projections to thalamus and the trigeminal nucleus (Noseda et al 2010) and may explain the paradoxical photosensitivity in patients blinded by photoreceptor loss. To characterize this reflex, the EMG, pupil movement and skin conductance were recorded to increasing red and blue light stimuli.

Methods: : Eight subjects were tested under both scotopic and photopic conditions using red (640nm) and blue (485nm) Ganzfeld, full field light, one second in duration, over a 6 log unit range of intensity (0.5 log unit steps). Time-stamped, computerized recording of the pupil, orbicularis and procerus muscle EMG, and skin conductance were measured simultaneously.

Results: : The EMG showed a linear increase with log unit light intensity in parallel with pupil responses, but with a threshold approximately 3 log units less sensitive. At the brightest light intensities, an involuntary reflex blink was also triggered. Similar to pupil responses, the EMG showed a sustained, prolonged response to bright blue light stimuli, consistent with intrinsic activation of melanopsin containing retinal ganglion cells. Subjects with the largest light-induced EMG responses also had the largest changes in skin conductance

Conclusions: : This study provides the first physiological evidence in humans that the light induced EMG response is mediated by melanopsin containing retinal ganglion cells, providing input to the trigeminal sensory nucleus, which then stimulates efferent output from the facial nucleus (as evidenced by EMG responses of orbicularis and procerus muscles) and sympathetic nervous system (as evidenced by increases in skin conductance). This unique light reflex may be useful in monitoring afferent light input affected by retinal and optic nerve disorders and also in diagnosing photosensitivity due to either ocular or central causes.

Keywords: electrophysiology: clinical • ganglion cells • eyelid 
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