VF - Binocular Eye Movement - Week 6 Flashcards
Define version.
Conjugate motion of the eyes to various locations.
Define yoked/conjugate muscles and give an example.
Describe what law this is.
Muscles that are equal, and must receive equal innervation for a given non-vergence movement.
Left lateral rectus and right medial rectus.
This is hering’s law of equal innervation.
In what instance does herings law not apply?
Vergence
Describe the stimuli for vergence, and where on the retina the images of far and near objects fall.
Target fixation images fall on the fovea. Images of targets further than the fixation fall on the nasal retina, whilst close targets fall on the temporal retina.
This is known as retinal disparity and is the stimuli for vergence.
Describe the fusion reflex. What triggers it?
It is the innate desire to make double images single. Most occurs when an object moves towards or away along the midline.
Name 3 components od the near triad.
Vergence
Accomodation
Pupillary constriction
Define synkinesis.
When a covered eye’s pupil constricts, accommodates and converges when the uncovered eye focuses on an object up close.
Define dark vergence, and what a normal dark fixation distance would be.
The position of the eyes in the absence of light.
Typically 1m.
Define proximal vergence.
Voluntary control of vergence.
Define instrument convergence.
Proximal vergence that occurs when looking through a telescope or microscope, that are focused at infinity.
Do vergence movements have a phasic and tonic component like saccades do?
Yes
Name a problem with Herings law.
Describe a possible explanation.
Fixation at targets that require unequal saccade components to reach. Herings law says they must be conjugate however.
Possble the system is more chameleon-like.
Motor neuron organisation take monocular cell output, and conjugate commands.
