Ocular Movements Flashcards by Haley Rambo

Movement or rotation of one eye around the axes of Fick (monocular).

Duction

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Binocular, simultaneous and conjugate eye movements or rotation of both eyes.

Version

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What are conjugate eye movements?

this is a binocular movement where the visual axis of both eyes are in the same direction to maintain fixation with both eyes. Both eyes move in the same direction, by the same amount.

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What is conjugate torsion?

twists the eyes in the same direction, clockwise or counterclockwise when the head is tilted to the right or left.

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disconjugate eye movement where the eyes (the visual axes) rotate in opposite directions.

Vergence

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Explain convergence

both eyes rotate in to maintain binocular fixation. For instance when reading. Medial rectus in each eye is yoked to produce this. Hering Law applies here.

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Explain divergence

both eyes rotate out. Lateral rectus in each eye is yoked. Incyclovergence: rotation of superior portion of both eyes in Excyclovergence: rotation of superior portion of both eyes out

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What are vergences important for?

Fusion

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What is meant by temporal characteristics?

both version and vergences have similar

latencies (about 120 – 200 ms) = how quick you start following a target

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What is meant by latency b/w version and vergences?

This is the time between the presentation

of a stimulus and the start of the movement.

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Between versions and vergences, which movement is faster?

Versions are faster acting movements while vergences are slower.
(Vergences are where your eyes are moving in opp directions)

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include the cranial nerves responsible for eye movements (3, 4 & 6) and the muscles they innervate (all the rectus and oblique muscles).

Infranuclear controls

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the cranial nuclei. Location of other visual motor pathways are in relation to the cranial nuclei.

Nuclear controls

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the higher order sensory and motor system that plans and controls the eye movements.

Supranuclear controls

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What do the supranuclear controls involve?

the neural network in the cerebral cortex, cerebellum and brainstem.

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Versions and vergences are controlled by what pathway?

Supranuclear pathway

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Versions; which direction do your eyes move?

Together

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Vergences; which direction do your eyes move?

Opposite directions

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Both eyes moving together in the same direction

Versions

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Fast conjugate eye movements for refixation

Saccades

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What occurs when an img is on the retinal periphery and the person wants to hold attention?

Swift movements to place and keep images on the fovea and/or to move from one image to another (saccades)

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What are saccades used for?

to correct the position error between the target and the fovea

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What is saccade latency?

the time between stimulus and response, is 120 – 200ms It has an accelerating and decelerating phase

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When are saccades well developed?

By 1 year of age

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Examples of saccadic eye movements

- Response to commands -Fast phase during optokinetic or vestibular movements - Rapid eye movements (REM) during sleep - Correcting saccades during fast pursuits Microsaccades

Regarding speed, are saccades faster or slower than pursuits and vergences?

Faster

Are saccades voluntary or involuntary?

Voluntary, but there can be reflex saccades with sudden visual, auditory or peripheral stimuli

What is an example of a version?

Pursuits b/c target is slowly moving

What's the latency of pursuits?

Shorter latency than saccades, meaning it's quicker to start

Relative target speed of pursuits

Pretty slow

What are pursuits?

- following eye movements | - It maintains the fovea conjugately on a slowly moving target. Stimulus is a target moving in the parafovea.

Are pursuits are voluntary or involuntary?

involuntary optokinetic movements to track a moving object and then refixate with a compensatory saccade to refixate.

Smooth pursuits are better developed by what time in life?

3rd to 4th month of life.

Where do pursuits hold the image on in the eye?

Holds img of slow moving target on fovea

What is wrong when pt can't do the voluntary movements (pursuits and saccades), but the pt can do involuntary ocular movements (vestibulo-ocular reflex = VOR)

Supranuclear gaze palsy

By what are pursuits controlled?

by ipsilateral parietal lobe, e.g. Right pursuit driven by Right parietal lobe.

When do VOR movements stabilize a retinal img?

During brief head movements

Is VOR a vergence or version?

Version

Is there a stimulus required for VOR?

No; can occur with eyes closed and even in the dark

When is Horizontal VOR developed?

At birth

When is vertical VOR developed?

Later in life (maybe about 1 yr old)

What can vestibular damage cause?

Horizontal nystagmus

What is the magnitude and direction of eyes vs head movement for VOR?

VOR produces eye movement of equal magnitude to head movement but in opposite direction

What kind of patients are the Doll's head maneuver's useful in?

Patients that are too young, uncooperative, too sick to respond to extraocular muscle testing, or unconscious

When would be a good time you would use the doll's head maneuver?

When vestibular dysfunction is suspected

When is the doll's head maneuver contraindicated?

In trauma patients with possible cervical spine injuries

If doll's head movement is contraindicated, what test will you do to provoke the VOR?

Caloric testing

What is caloric testing?

uses warm and cold water to set up temperature gradients in the semicircular canal causing a convection current in the endolymph then stimulating the hair cells.

What angle does the patient's head need to be at in order to do caloric testing?

30 degrees

With cold water for caloric testing, what is the normal response?

nystagmus with fast phase towards the opposite ear.

With warm water for caloric testing, what is the normal response?

Fast phase towards the ipsilateral ear

What is an optokinetic reflex responsible for?

-continuous eye movements after | brief head movements (ex: VOR)

When does optokinetic reflex take over?

After a brief head movement (after VOR is over) b/c of prolonged head movements

When does the optokinetic reflex hold the img steady on the retina?

During sustained head movements

What is rotational testing?

the patient is slowly rotated in a chair for about 20 seconds. The doctor pays attention to the eyes .

What's the normal response for optokinetic reflexes and rotational testing?

- Slow conjugate eye movements | - then fast phase opposite the rotation of the chair

Slow pursuit eye movement followed by a fast corrective saccade because a visual field moves over the retina (Version)

Optokinetic nystagmus (OKN)

What's the fast corrective saccade for OKN?

To fixate on a new stripe

What kind of latency is there for OKN?

Longer latency

Is there a response from the visual system for OKN?

Yes, unlike VOR

What kind of movement is OKN?

Conjugate movement maintaining the img of the moving target on the fovea when the head is still

When is OKN developed?

3-5 months of age

What does positive OKN response mean?

VA is at or better than the size of the stripes (the visual motor pathway is intact)

What is a negative response of OKN?

Inconclusive

OKN slow phase is in what direction?

In the direction of the drum rotation

How do you perform the OKN test?

- pt is seated - hold drum at eye level - 40-50 cm from pt - tell pt to look at stripes - test at both horizontal and vertical - spin drum at steady speed

What is an asymetrical nystagmus on OKN testing respresent?

Neurological disorder, functional or developmental problems

Who should be able to sustain fixation for 10 seconds during OKN testing?

All patients, except very young, anxious, hyperactive and/or inattentive patients

4 different evaluations of saccadic eye movements

- NSUCO - Developmental Eye Movement (DEM) - King Devick - Visagraph

2 different evaluations of pursuits

NSUCO | Groffman Tracings

What are vergences important for?

to ensure bifoveal fusion and eliminate diplopia that could occur because of images falling on retinal points that do not correspond.

When do "compensatory" fusional movements occur?

When the disparity exceeds that Panum's fusion area. A sensory and motor fusion occurs.

What is Panum's fusion area, and what does it allow if not exceeded?

a zone of disparity, if not exceeded, still allows fusion of disparate points.

4 types of vergences

Tonic Proximal Fusional Accommodative

Vergence that requires attention and cooperation of the cerebral cortex b/c of a disparity or a variation in the images at the retina

Fusional vergences

Example: when an object is moving away or towards you, the retinal images are shifted off the corresponding retinal points – so the eyes move to correct the disparity and get the images back on the corresponding retinal points.

Fusional vergences

Vergence that requires constant innervation tone to the extraocular muscles when awake and alert

Tonic vergence

Naturally because of the anatomy of the orbit, what's the position of the eye due to tonic vergence?

Eyes are divergent as we can see in unconscious patients

When are tonic vergences needed?

To hold eyes straight when eyes are at rest

Vergence where there's induced convergence movement due to the awareness of near

Proximal (con)vergence

Vergence where there's a consistent increment of accommodative convergence that happens with each diopter of accommodation, giving the AC/A ration

Accomodative vergence

Abnormally high AC/A can produce what?

ET with accommodation | Accommodative vergence

What can abnormally low AC/A make it harder to do?

Converge, less esotropic, more exotropic (accommodative vergences)