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Related Experiment Videos

Ocular accomodative changes in humans induced by positional changes with respect to gravity.

C H Markham, S G Diamond, N E Simpson

    Electroencephalography and Clinical Neurophysiology
    |March 1, 1977
    PubMed
    Summary
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    Human eye accommodation changes during head rotation, suggesting a link between the vestibular system (utricles) and visual focus. This response is sensitive to rotational direction and magnitude.

    Area of Science:

    • Vestibular Neuroscience
    • Ophthalmology
    • Human Physiology

    Background:

    • Ocular accommodation is crucial for clear vision at varying distances.
    • The vestibular system, particularly the otolith organs (utricles and saccules), detects linear acceleration and head orientation.
    • Previous research has not extensively explored the direct influence of controlled head rotation on ocular accommodation.

    Purpose of the Study:

    • To investigate the effect of controlled head rotation on ocular accommodation in human subjects.
    • To determine if the direction and degree of naso-occipital axis rotation influence accommodative responses.
    • To explore the potential role of the vestibular system, specifically the utricles, in mediating these changes.

    Main Methods:

    • Ocular accommodation was measured in 16 healthy human subjects.

    Related Experiment Videos

  • Subjects underwent controlled rotation (1 degree/sec) about their naso-occipital axes.
  • Rotations included both ipsilateral and contralateral movements relative to the observed eye, with varying degrees of complete and partial revolutions.

    • Main Results:

    • Rotation ipsilateral to the observed eye induced accommodative (lens-thickening) changes, beginning around 14 degrees and peaking by 45 degrees.
    • Contralateral rotation initially showed minimal change, with significant accommodation occurring after 135 degrees, peaking around 270 degrees.
    • The observed accommodative responses showed a threshold similar to that of linear acceleration detection.

    Conclusions:

    • Head rotation about the naso-occipital axis significantly impacts ocular accommodation.
    • The utricles, oriented horizontally, are likely involved in this vestibular-driven accommodative reflex.
    • The findings suggest a functional link between the vestibular system's perception of head orientation and the eye's focusing mechanism.