eye movements—donna l. hill, m.d., uf and shands jacksonville

Eye MovementsEye Movements

Donna L. Hill, MDDonna L. Hill, MDNeuro-ophthalmologyNeuro-ophthalmology

Departments of Neurology Departments of Neurology and Ophthalmologyand Ophthalmology

UF&Shands JacksonvilleUF&Shands Jacksonville

Normal Eye MovementsNormal Eye Movements

• Objective: FoveationObjective: Foveation• Extraocular musclesExtraocular muscles• Muscle innervation – CNs III, IV, and VIMuscle innervation – CNs III, IV, and VI• Cranial nerve nucleiCranial nerve nuclei• Three primary types of movementsThree primary types of movements• Pathologic eye movementsPathologic eye movements

Objective: foveationObjective: foveation

• fovea – most sensitive portion of retinafovea – most sensitive portion of retina

• we need to orient, either voluntarily or we need to orient, either voluntarily or reflexively, to important stimulireflexively, to important stimuli

• accomplished by directing our eyes to a target accomplished by directing our eyes to a target so that it is projected onto the foveaso that it is projected onto the fovea

• to maintain foveation, we depend on to maintain foveation, we depend on visual visual feedbackfeedback as the primary source of as the primary source of information on eye movement accuracyinformation on eye movement accuracy

Extraocular muscles Extraocular muscles • Superior rectus – moves eye up Superior rectus – moves eye up

• Inferior rectus – moves eye down Inferior rectus – moves eye down

• Medial rectus – moves eye in (a-d-duction)Medial rectus – moves eye in (a-d-duction)

• Lateral rectus – moves eye out (a-b-duction)Lateral rectus – moves eye out (a-b-duction)

• Inferior oblique – moves eye up when it is in an adducted position; Inferior oblique – moves eye up when it is in an adducted position; also extorts the eye.also extorts the eye.

• Superior oblique – moves eye down when it is adducted; also intorts Superior oblique – moves eye down when it is adducted; also intorts the eye.the eye.

left

Isolating Extraocular MusclesIsolating Extraocular Muscles

CN IIICN III

CN IIICN III• Superior division

- Superior rectus muscle- Levator palpebrae superioris muscle

• Inferior division- Medial rectus muscle- Inferior rectus muscle- Inferior oblique muscle- Parasympathetic innervation to pupil

CN IV CN IV CN VICN VI

CN VICN VI

Coordination of Eye MovementsCoordination of Eye Movements

• Separate systems exist to control each different Separate systems exist to control each different subtype of eye movement: saccades, smooth subtype of eye movement: saccades, smooth pursuit, and vergencepursuit, and vergence

• May be nuclear or supranuclear controlMay be nuclear or supranuclear control

• May be reflexive or voluntaryMay be reflexive or voluntary

• Separate systems exist to govern vertical and Separate systems exist to govern vertical and horizontal eye movementshorizontal eye movements

Targeting Eye MovementsTargeting Eye Movements

1.1. Saccades: Quick, darting conjugate Saccades: Quick, darting conjugate movements which direct the eyes to a new movements which direct the eyes to a new target.target.

2.2. Smooth pursuit: A slower conjugate movement Smooth pursuit: A slower conjugate movement which allows for tracking of a moving object, or which allows for tracking of a moving object, or of a stationary object while we are moving.of a stationary object while we are moving.

3.3. Convergence: A dysconjugate movement of Convergence: A dysconjugate movement of both eyes toward the midline to allow for both eyes toward the midline to allow for focusing on a near object by adjusting the angle focusing on a near object by adjusting the angle between the eyes.between the eyes.

Variety of pathways contribute to saccadic Variety of pathways contribute to saccadic control and smooth pursuitcontrol and smooth pursuit

SaccadesSaccades

• Under the control of three different areas Under the control of three different areas in the brain:in the brain:– voluntary saccades - frontal eye f ields voluntary saccades - frontal eye f ields

(Brodmann’s area 8)(Brodmann’s area 8)

– reflexive saccades to complex stimuli - ref lexive saccades to complex stimuli - parietal lobes (Brodmann’s area 7) parietal lobes (Brodmann’s area 7)

– ref lexive saccades to elementary st imuli - ref lexive saccades to elementary st imuli - superior coll icul isuperior coll icul i

Voluntary Saccades (Voluntary Saccades (horizontal)horizontal)

results in results in saccade to saccade to

contralateral contralateral spacespace

CEREBRAL HEMISPHERE

MIDBRAIN

PONS

PPRF PPRF

VI VI

FEF FEF

IIIIII

Voluntary Horizontal SaccadesVoluntary Horizontal Saccades

MIDBRAIN

PONS

VI VI

IIIIII

LR MR MR LR

Yoking MechanismYoking Mechanism

Reflexive Saccades Reflexive Saccades

- to complex stimuli originates in area 7 of the parietal lobe

- to elementary stimuli originates in superior colliculi

dorsolateral prefrontal cortex involved in planning of eye mvts

Smooth PursuitSmooth Pursuit

Two types:Two types:1.1. Voluntary (actually termed “smooth pursuit”) Voluntary (actually termed “smooth pursuit”)

movements - originate in the temporo-movements - originate in the temporo-parietal lobeparietal lobe

2.2. Reflexive - which are under vestibular Reflexive - which are under vestibular nuclear control alone and constitute what is nuclear control alone and constitute what is called the vestibulo-ocular reflex (VOR).called the vestibulo-ocular reflex (VOR).

Voluntary Voluntary Smooth PursuitSmooth Pursuit

• originates near the angular originates near the angular gyrus - Area 39 at the temporal gyrus - Area 39 at the temporal parietal occipital junctionparietal occipital junction

• cells in this region are able to cells in this region are able to compute the speed and compute the speed and direction of a moving objectdirection of a moving object

• results in ipsilateral smooth results in ipsilateral smooth pursuitpursuit

IPSI

Optokinetic ReflexOptokinetic Reflex

• Combination of saccades and Combination of saccades and smooth pursuit that allow tracking smooth pursuit that allow tracking of targets in turn (e.g. counting of targets in turn (e.g. counting sheep as they jump over a fence).sheep as they jump over a fence).

• smoothly pursue one target, then smoothly pursue one target, then saccade in the opposite direction saccade in the opposite direction to pick up the next targetto pick up the next target

• parieto-temporal junction (smooth parieto-temporal junction (smooth pursuit area) projects down to pursuit area) projects down to ipsilateral vestibular nucleus, ipsilateral vestibular nucleus, inhibits it allowing ipsilateral inhibits it allowing ipsilateral smooth pursuitsmooth pursuit

• then, the FEF of the then, the FEF of the samesame hemisphere generates a saccade hemisphere generates a saccade back (contralateral) to the next back (contralateral) to the next targettarget

Reflexive Smooth Pursuit - VORReflexive Smooth Pursuit - VOR

• maintains gaze on a maintains gaze on a target despite head target despite head movementmovement

• reflex arc – reflex arc – semicircular canal semicircular canal opposite the head turn opposite the head turn detects motion and detects motion and activates the ipsi activates the ipsi vestibular n. which vestibular n. which deactivates its deactivates its inhibitory input on the inhibitory input on the ipsilateral VIipsilateral VI

• results in eyes turning results in eyes turning opposite to the head opposite to the head turnturn

VIII

deactivates (-) input

p339 Medical Neuroscience, Nadeau et al

ConvergenceConvergence

• When areas of the occipital cortex detect a When areas of the occipital cortex detect a discrepancy in the retinal projection from each discrepancy in the retinal projection from each eye and amount of blur, a signal is sent to eye and amount of blur, a signal is sent to initiate convergence. initiate convergence.

• To bring a near object into focus actually To bring a near object into focus actually involves convergence, accomodation (lens involves convergence, accomodation (lens curvature increases) and pupillary constriction. curvature increases) and pupillary constriction. Together, these 3 movements are called the Together, these 3 movements are called the near triad.near triad.

Pathologic eye movementsPathologic eye movements

• MuscleMuscle– Trauma, entrapment, inflammation, infiltrating diseasesTrauma, entrapment, inflammation, infiltrating diseases

• Neuromuscular Junction Neuromuscular Junction – myasthenia gravis, botulism, organophosphate poisoningmyasthenia gravis, botulism, organophosphate poisoning

• Cranial nuclei or nerveCranial nuclei or nerve– Brainstem: stroke, hemorrhage, multiple sclerosis, tumor, traumaBrainstem: stroke, hemorrhage, multiple sclerosis, tumor, trauma– Subarachnoid space: Increased intracranial pressure, aneurysm, Subarachnoid space: Increased intracranial pressure, aneurysm,

meningitis, sarcoidosis, autoimmunemeningitis, sarcoidosis, autoimmune– Cavernous sinus: Tumor, sinus thrombosis, pituitary apoplexy, Cavernous sinus: Tumor, sinus thrombosis, pituitary apoplexy,

sphenoid sinusitis, carotid-cavernous fistula, Tolosa-Hunt sphenoid sinusitis, carotid-cavernous fistula, Tolosa-Hunt syndromesyndrome

– Orbit: Trauma, tumor, infectionOrbit: Trauma, tumor, infection

right cranial nerve III palsyright cranial nerve III palsy

right cranial nerve VI palsyright cranial nerve VI palsy

Gaze PalsyGaze Palsy

• inability to look in a particular direction (ie. inability to look in a particular direction (ie. neither eye can look right)neither eye can look right)

• lesion in the FEF, the PPRF, or the CN VI lesion in the FEF, the PPRF, or the CN VI nucleus nucleus – Lesion in the FEF – unable to look contralaterally, Lesion in the FEF – unable to look contralaterally,

eyes deviate toward the lesion, can be overcome with eyes deviate toward the lesion, can be overcome with VORVOR

– Lesion in PPRF or CN VI nucleus – inability to look Lesion in PPRF or CN VI nucleus – inability to look ipsilaterally with either eyeipsilaterally with either eye

CEREBRAL HEMISPHERE

MIDBRAIN

PONS

PPRF PPRF

VI VI

FEF FEF

IIIIII

Voluntary Horizontal SaccadesVoluntary Horizontal Saccades

Left MLF lesion – intranuclear ophthalmoplegiaLeft MLF lesion – intranuclear ophthalmoplegia

MIDBRAIN

PONS

VI VI

IIIIII

LR MR MR LR

Yoking MechanismYoking Mechanism

• Dr. Tariq Bhatti and his patients for clinical imagesDr. Tariq Bhatti and his patients for clinical images• Dr. Angela McSwain, Dr. Nadeau’s text, Peter Duus ( “Topical Diagnosis in Dr. Angela McSwain, Dr. Nadeau’s text, Peter Duus ( “Topical Diagnosis in

Neurology”), and Frank H. Netter (Ciba Collection of Medical Illustrations, Vol 1)Neurology”), and Frank H. Netter (Ciba Collection of Medical Illustrations, Vol 1)• Dr. Nancy Newman and Dr. Valerie Biousse, Neuro-ophthalmology Emory Dr. Nancy Newman and Dr. Valerie Biousse, Neuro-ophthalmology Emory

UniversityUniversity

AcknowlegdementsAcknowlegdements