Survey of Ophthalmology
Volume 47, Issue 1 , Pages 17-26, January 2002

The Eye as Metronome of the Body

  • Virginia Lubkin, MD

      Affiliations

    • New York Eye and Ear Infirmary, New York, NY USA
    • ,
  • Pouneh Beizai, MD

      Affiliations

    • Jules Stein Eye Institute, UCLA School of Medicine, Los Angeles, CA USA
    • ,
  • Alfredo A Sadun, MD, PhD

      Affiliations

    • Doheny Eye Institute, USC School of Medicine, Los Angeles, CA, USA
    • Corresponding Author InformationReprint address: Alfredo A. Sadun, MD, PhD, Thornton Professor of Vision, Doheny Eye Institute-DOH 5802, 1450 San Pablo St., Los Angeles, CA 90033-4671

Abstract 

Vision is much more than just resolving small objects. In fact, the eye sends visual information to the brain that is not consciously perceived. One such pathway entails visual information to the hypothalamus. The retinohypothalamic tract (RHT) mediates light entrainment of circadian rhythms. Retinofugal fibers project to several nuclei of the hypothalamus. These and further projections to the pineal via the sympathetic system provide the anatomical substrate for the neuro-endocrine control of diurnal and longer rhythms. Without the influence of light and dark, many rhythms desynchronize and exhibit free-running periods of approximately 24.2–24.9 hours in humans. This review will demonstrate the mechanism by which the RHT synchronizes circadian rhythms and the importance of preserving light perception in those persons with impending visual loss.

Keywords:  circadian rhythms, diurnal rhythms, light entrainment, retinohyopothamic tract, vision

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PII: S0039-6257(01)00282-X

Survey of Ophthalmology
Volume 47, Issue 1 , Pages 17-26, January 2002

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