MOVEMENTS OF EYE Physiology Lecture SlideshowMOVEMENTS OF EYE Physiology Lecture Slideshow

Muscular Movements Of Eye

  • Three pairs of muscle
    – Medial and lateral recti
  • Move side by side
    – Superior and inferior recti
  • Move eyeball up and down
    – Superior and inferior oblique
  • Rotate the eyeball
  • Nuclei of nerves supplying extraocular are present in brainstem
  • Neural connection by medial longitudenal fasiculus
  • Cortical control of oculomotor apparatus to occipital lobe
  • By
    – Occipitotectal tract– to pretectal area
    – Occipitocollicular tract– to superior colliculus
  • Body equilibrium control to oculomotor system(vestibular
    nuclei via medial longitudenal fasiculus)

Fixation Movements

  • Eye to fix on a discrete portion of field of vision
    – Involuntary fixation mechanisms
    – Voluntary fixation mechanisms

Voluntary fixation movements

  • Voluntary fixation movements are controlled by
    – Bilaterally in premotor field of frontal cortex
  • Lesion to the area leads to locking at one point of fixation and
    unable to move to other
  • fixation mechanism “lock” on the object of focus– controlled
    by secondary visual areas in the occipital cortex
  • located mainly anterior to the primary visual cortex
  • Lesion of fixation area is destroyed bilaterally fixation become
    partially or completely

Involuntary fixation movements

  • Three types of continuous involuntary movements
  1. Continuous tremor (30-80 cycles/sec)
    Caused by successive contractions of motor units in ocular muscles
  2. Slow drift of the eyeballs in either direction
  3. Sudden flicking movements
  • Spot of light fixed on the foveal region of retina
  • Tremulous movements move the spot at a rapid rate
  • Drifting movements cause slow movement across the cones
  • As the image move to the periphery flickering movement
    suddenly brings it back to the center
  • Automatic response moves the image back toward the central
    point of vision

Saccidic Movements

  • Visual scene is moving requires fixation on every other point in
    visual field
  • Jumping of focus from one to the next at a rate of two to three
    jumps per second—saccades
  • Movements– opticokinetic movements
  • Rapidity of saccades 10% of time is spent in moving the eyes
  • 90% of the time being allocated to the fixation sites

Pursuit Movement

  • Eyes remain fixed on a moving object—pursuit movement
  • Cortical mechanism automatically detects the movement of
    object and develops same change in the eye
  • Object is moving up and down in a wavelike form initially eye is
    unable to fixate it within few seconds image perception
    becomes smooth
  • High degree of automatic subconscious computational ability
    by the pursuit system for controlling eye movements

Superior Colliculi

  • Involuntary fixation mechanism
  • Turning the eyes and head toward a visual disturbance

Analysis Of Visual Information

  1. The Fast “Position” and “Motion” Pathway
  2. The Accurate Color Pathway
  • Analysis of Third-Dimensional Position, Gross Form, and Motion
    of Objects
  • third-dimensional positions of visual objects in space
    – Overlap with somatic association area
  • gross physical form of the visual scene and movement
    – Y ganglion cells but no color
  • From primary visual cortex signals move to posterior midtemporal
    area and occipitoparietal cortex.

Analysis of visual color and detail

  • Signals from primary visual cortex into secondary visual areas
    of the inferior, ventral, and medial regions of the occipital and
    temporal cortex
  • analysis of visual detail and color
  • pathway also tells about recognizing letters, reading, texture of
  • Analysis of the information

Analysis of Contrasts in the Visual Image

  • Areas of maximum excitation occur along the sharp borders of
    the visual pattern
  • Intensity of stimulation is directly proportional to contrast

Analysis of direction in the Visual Image

  • Simple Cells – Orientation of Lines and Borders and colors
    – Present in layer IV
  • Complex Cells – Line is displaced laterally or vertically in the
    Visual Field
    – Complex contrasts are detected by these cells


  • Squint or Cross-eye
  • Lack of fusion of the eyes
  • Abnormally set patterns of conjugate movements
  • Suppression of image from a repressed eye


  • Permanent loss of vision with out organic disease in children
    (up to 6 years )
  • Strabismus
  • Severe refractive errors at birth

Horner Syndrome

  • Interruption in sympathetic fibers– cervical sympathetic chain
  • Fibers to dilator pupillae are interrupted—constriction of pupil
  • Drooping of eyelid– smooth muscles in upperlid, innervated by
  • Blood vessels of corresponding side are dilated
  • Sweating doesn’t occur on affected side

Argyll Robertson Pupil

  • Final nerve fibers in the pathway through the pretectal area to
    the Edinger-Westphal nucleus –Inhibitory type
  • inhibitory effect is lost, the nucleus become active, pupils
    remain constricted, failure to respond to light
  • Cause: Syphilis
  • Respond to accommodation reflex but not to light reflex

Autonomic Control of Eye

  • Parasympathetic Nerves
  • Control focusing – Cilary muscles
  • Constrict pupil – Sphincter of iris
  • Sympathetic Nerves
  • Radial fibers of iris – Dilates pupil
    Control of Pupillary Diameter
  • Miosis – constriction – 1.5 mm
  • Mydriasis – dilation – 8 mm

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