Conjugated movements of the eye

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Conjugated movements of the eye

Basics

Coordination of eye movements requires the collaboration of cortical association areas and cranial nerve nuclei in the midbrain and pons. It is essential for the following tasks:

  • Fast conjugated tracking of moving objects (saccadic)
  • Slow tracking of moving objects (pursuit)
  • Alignment of both eyes to track a target that moves closer or further away (convergence)
  • Usage of vestibular signals to move the eyes in an equal and opposite direction if the viewer's head or body moves (vestibulo-ocular)

Non-visually guided saccades

The neural pathway in coordinating non-visually guided saccadic eye movement is as follows:

  • Association areas in cortex send descending fibres to synapse in the contralateral paramedian pontine nucleus of the reticular formation (PPRF) in the brain stem
  • From PPRF, an interneuron relays signal to the left abducens nucleus, which in turn sends a signal simultaneously to:
    • the left lateral rectus muscle to abduct the left eye
    • the right oculomotor nucleus via the medial longitudinal fasciculus (MLF)
    • the right oculomotor nucleus in turn signals
      • the right medial rectus muscle for adduction of the right eye

Visually guided saccades

For visually guided saccadic movement, the initial command comes from the visual areas of the occipital lobe (e.g., telling the patient to stare at the tip of the ball-point pen on the left side without head movement).