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Terms in this set (40)
Foveation is the movement of the eyes so the foveas of both eyes are amed at a common point of interest.
What is foveation?
Fast, ballistic movements, used for target location.
What is saccadic eye movement?
Tracking movement, used to follow a moving object.
What is smooth pursuit movement?
When the eyes move in response to head rotation, used to keep an object in view as the head moves.
What is vestibulo-oculomotor movement?
Vergence movement is when the eyes move together or apart as the target moves closer or farther away.
What is vergence movement?
Oculomotor, trochelar, and abducens.
What are the three nuclei responsible for controlling movement of the eyes?
Saccadic: ballistic, rate of movement is constant, duration depends on distance the eye is to move.
Smooth pursuit: slower tracking movements, requires a moving target, speed matches target speed.
Differentiate between saccadic movement and smooth pursuit movement.
When both eyes move in the same direction at the same time.
What is conjugate eye movement?
When a foveated target moves toward or away from the viewer, and the eyes move in a disconjugate manner to accomodate this changing distance to maintain foveation.
What is disconjugate/vergence eye movement?
A type of disconjugate movement, when eyes turn nasally as objects approach the head.
What is convergent eye movement?
A type of disconjugate eye movement, both eyes turn outward to maintain foveation on an object moving away from the head.
What is divergent eye movement?
Occurs when saccades (fast phase) alternate with smooth pursuits (slow phase).
Equidistant trees passing by while you're driving on the highway, and you're tracking each one.
Used to test visual acuity.
What is optokinetic nystagmus?
Nasal: anterior of eye pulled medially
Temporal: anterior of eye pulled laterally
Superior: anterior of eye pulled superiorly
Inferior: anterior of eye pulled inferiorly
Intorsion: superior pole of eye pulled medially
Extorsion: inferior pole of eye pulled medially
What are the planes of motion for the eye?
Action: abduction of eye (pull laterally/temporally)
Nerve: abducens nerve, CN VI (6)
Lateral rectus, action and innervation.
Action: adduction of the eye (pull medially/nasally)
Nerve: Oculomotor nerve, CN III (3)
Medial rectus, action and innervation
Action: Elevetion and intorsion
Nerve: Oculomotor nerve
Superior rectus, action and innervation
Action: Depression and extorsion
Nerve: Oculomotor nerve
Inferior rectus, action and innervation
Action: Elevation and extorsion
Nerve: Oculomotor nerve
Inferior oblique, action and innervation
Action: Depression and intorsion
Nerve: Trochelar nerve CN IV (4)
Superior oblique, action and innervation
Contralateral: Trochlear nerve CN 4
Ipsilateral: Oculomotor CN 3 and Abducens CN 6
Which ocular nerve controls the contralateral eye? Ipsilateral?
Oculomotor nerve palsy
Injury to CN 3 causes what?
The affected eye can only move outward and down
Pupil is dilated and unresponsive to light
Ptosis: eyelid droops
Diplopia: double vision
What are the symptoms of oculomotor nerve palsy?
What causes oculomotor nerve palsy?
Trochlear nerve palsy
Affects superior oblique m.
Damage to CN 4 causes what?
Extorsion of affected eye with slight upward gaze
Patients carry their head tildet down and away from the affected side to correct the sense of hypertropia.
What are the symptoms of trochlear nerve palsy?
Causes of trochlear nerve palsy?
Abducens nerve palsy
Affects lateral rectus muscle
Damage to CN 6 causes what?
Affected eye cannot abduct/move temporally, producing binocular horizondal diplopia.
Patient presents with slight head turn toward affected eye
What are the symptoms of abducens nerve palsy?
What causes abducens nerve palsy?
Activation of PPRF causes ipsilateral contraction of lateral rectus muscle.
Causes contralateral contraction of medial rectus muscle.
Organizes conjugate horizontal gaze toward same side.
What is the function of the paramedian pontine reticular formation PPRF?
Controls vertical gaze
Ventral part of complex mediates "down" gaze, dorsal mediates "up" gaze.
What is the function of the rostral midbrain reticular formation RMRF?
Receives visual input to locate objects and programs saccades to move eyes to new fixations.
What is the function of the superior colliculus?
They fire when a tracked target moves to a new position.
Superficial layer is a highly isomorphic, point-by-point map of the visual field represented contralaterally.
What do the cells in the superficial layer of the superior colliculus do?
They fire prior to initiating a saccade to track the recently moved object.
Cells in the superficial layer excite the motor cells.
What do the cells in the deep layer of the superior colliculus do?
Auditory, visual, and tactile stimulation are integrated by the superior colliculus to process spatial relationships.
A visual target that also emits a sound and touches the person elicits a much stronger response than either seeing or hearing it alone.
Explain the additive effect of auditory and tactile stimulation to the function of the superior colliculus.
What tract enables the head to match eye movements?
A loss of ability to mace saccades in the contralateral visual field.
A lesion in one superior colliculus causes what?
Contains the smooth pursuit system, enabling smooth pursuit eye movement.
What does the parieto-occipital area of the cerebral cortex do?
Initiates voluntary conjugate eye movements, particularly saccades, for contralateral visual fields.
What does the frontal eye field of the cerebral cortex do?
Performs computations essential to visual tracking.
Damage to visual cortex in occipital lobe makes smooth pursuit movements impossible.
What does the visual cortex do?
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