Ocular movements Flashcards
The movement or rotation of one eye around the axes of fick
Duction
Binocular, simultaneous and conjugate eye movements or rotation of both eyes.
Version
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)
Conjugate eye movements
Twists the eyes in the same direction, clockwise or counterclockwise when the head is tilted to the right or left.
Conjugate torsion
a disconjugate eye movement where the eyes rotate in opposite directions. (One eye moves right the other eye moves left)
Vergence
both eyes rotate in to maintain binocular fixation
Convergence
When you read what type of vergence are you having
Convergence
What type of law applies to convergence?
And what muscle is yoked to produce this?
Hering law
Medial rectus
Both eyes rotate out
Divergence
For divergence what muscle in each eye is yoked?
Lateral rectus
Rotation of superior portion of both eyes in (tip of OD goes in and the tip of OS goes in)
Incyclovergence
Rotation of superior portion of both eyes out
Excyclovergence
T/F: vergences are important for fusion
True
The time between the presentation of a stimulus and the start of the movement
Latency
Are versions faster or slower than vergences?
Faster
Are vergences faster or slower than versions?
Slower
these include the cranial nerves responsible for eye movements (3, 4, & 6) and the muscles they innervate (all the rectus and oblique muscles).
Infranuclear controls
Higher order sensory and motor system that plans and controls the eye movements.
Supranuclear controls
What control involves the neural network in the cerebral cortex, cerebellum and brainstem.
Supranuclear control
What control visual motor pathway are versions and vergences controlled by?
Supranuclear controls
What are the 5 types of versions?
- saccades
- pursuits
- VOR
- OKN
- OKR
Fast conjugate eye movements for refixation (on a new target) / swift movements to place and keep images on the fovea (brings image to the fovea)
Saccades
Are saccades voluntary or involuntary?
Voluntary
What is the speed of saccades?
400-700 degrees/sec
T/F: saccades require a strong force to move the eye rapidly in the globe against the viscosity on the orbit
True
What is the latency of a saccade?
120-200ms
When are saccades well developed?
1 year of age
Name 5 examples of saccadic eye movements?
- Response to commands
- Fast phase during optokinetic or vestibular movements
- REM
- Correcting saccades during fast pursuits
- Microsaccades
Are saccades faster than pursuits and vergences?
Yes
What is the peak velocity of pursuits?
30-60 degrees/sec
Eye following moving target to maintains image on the retina (fovea)
Pursuits
Do pursuits have a shorter or longer latency compared to saccades?
What is the latency (#)?
Shorter, so its faster to start
125msec
When are smooth pursuits better developed?
Month 3-4
Are pursuits voluntary or involuntary optokinetic movements?
Voluntary
What do pursuits help match?
Eye velocity to target velocity
What lobe controls pursuits?
Ipsilateral parietal lobe
Ex: right pursuit is driven by right parietal lobe
These movements stabilize a retinal image during brief head movement.
Vestibulo-ocular reflex (VOR)
Does VOR require stimuli?
No. You can do it with the eyes closed
Seen in the oculocephalic maneuver/doll’s head (moving the patient’s head up and down and side to side while asking them to maintain fixation).
VOR
When is the horizontal VOR well developed?
What about vertical?
Horizontal- at birth
Vertical-later
Doll head result is conjugate eye movements ___ to the head movement.
Opposite
What does vestibular damage cause?
Horizontal nystagmus
What are the results of a normal VOR?
Eye movements that are equal and opposite to the head movement
Do the patients have to be cooperative during VOR testing?
Nahhhhhh, they can be knocked the hell out
When do you not want to test VOR
In trauma patients with possible cervical spine injuries
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.
Caloric testing
When would you do caloric testing?
When dolls head cant be performed
For caloric testing, the patients head is angled…
30 degrees so the horizontal semicircular canal is perpendicular to the floor
With cold water injected what is the normal response?
Nystagmus with fast phase towards the opposite ear
What is the response for warm water injected in the ear?
Fast phase towards the ipsilateral ear
Responsible for continuous eye movements after
brief head movements/ maintains image during constant head rotation
Optokinetic reflex
When does the optokinetic reflex kick in?
After the VOR response fades because of prolonged head movement (more than 30-60 degrees/sec of movement)
Optokinetic reflex holds image of the world steady on the retina during_________
Sustained head movement
What is a way you can test OKR?
By slowly rotating the patient in a chair for ~20 secs while looking at the patients eyes
What is the normal response to OKR?
slow conjugate eye movement then fast phase
opposite the rotation of the chair.
Is OKR voluntary or involuntary?
Involuntary
Slow pursuit eye movement followed by a fast corrective saccade because a visual field moves over the retina.
Optokinetic Nystagmus (OKN)
A conjugate movement maintaining the image of the moving target on the fovea when the head is still
OKN
Does OKN require input from the visual system?
Yes
When does OKN develop?
3-5 months of age
OKN can be used for what kind of patients?
Malingering and uncooperative patients
What does a positive OKN response mean?
The VA is at or better than the size of the stripes (the visual motor pathway is intact)
What does a negative response mean?
That its inconclusive
How far do you hold the OKN drum? And how do you hold it
Hold it at eye level, ~40-50 cm from patient
Do you test the OKN at horizontal, vertical, or both?
Both
Is there a standard speed on the drum?
No
How long should patients be able to sustain fixation?
10 seconds
Who cant fixate for 10 seconds?
-young, anxious, hyperactive and/or inattentive patients
Ocular motor disorders can show…..
serious neurological, functional or developmental problems.
Why would children with difficulty reading have difficulty with pursuits and saccades
Because the smaller, more fixations, and regressions
What is the speed of OKN?
30-60 degrees/sec
Is OKN movements voluntary or involuntary?
Involuntary
The fast phase moves ____ of the OKN drum rotation
Opposite
Why are vergences important?
To ensure bifoveal fusion and eliminate diplopia that could occur because of images falling on retinal points that do not correspond.
When do vergences occur?
When the disparity exceeds panums fusion area
A zone of disparity, if not exceeded, still allows fusion of disparate points.
Panum’s fusion area
What are the 4 types of vergences
- tonic
- proximal
- fusional
- accommodative
This vergence requires attention and cooperation of the cerebral cortex
Fusional vergence
This fusional reflex is elicited because of a disparity or a variation in the images at the retina.
Fusional vergence
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 vergence
The vergence needed to hold eyes straight when eyes are at rest.
Tonic vergence
induced convergence movement due to the awareness of near (bringing the phoropter close to the patient)
Proximal vergence
A consistent increment of accommodative convergence happens with each diopter of accommodation giving the AC/A ratio.
Accommodative vergence
Abnormally high AC/A can produce___
ET with accommodation
Abnormally low AC/A makes it harder to ____
Converge, less esotropic, more exotropic
The the muscles do / due to the direction of its pull around the axes
Muscle action
Major effect on the position of the eye when the muscle contracts while the head is in primary position.
Primary action
The position of the eyes when fixating straight ahead. The eyes and head are both straight.
Primary position
Position around the X and Z axes of Fick (straight up, straight down, right gaze and left gaze).
Secondary position
T/F: the secondary position is purely vertical or horizontal.
True
The Y axis (the oblique muscle positions) as well as
head tilt positions.
Tertiary position
The positions where only 1 muscle in each eye is
responsible for movement
Cardinal positions
The gaze position (one of the cardinal positions) where the effect of a muscle is best observed. You can isolate and evaluate each muscle
Field of action
When the SR is abducted 23 degrees and the visual axis and muscle plane (at orbital axis) coincide it acts as an
Elevator
When the SR is adducted 67 degrees and the visual axis is perpendicular to muscle plane, the SR becomes an
Intortor
When the IR is abducted 23 degrees and the visual axis and muscle plane (at orbital axis) coincide it acts as an
Depressor
When the IR is adducted 67 degrees and the visual axis is perpendicular to muscle plane, the SR becomes an
Extortor
What is the best position to evaluate the SO?
when the eye is adducted 51 degrees, the visual axis and the direction of pull/muscle plane coincide)
Any weakness of the superior oblique can be seen as a failure to….
depression in adduction
What is our RSR field of action?
up to the right (abducted), but the actions of the
SR are elevation, intorsion and adduction!
The muscle plane/insertion of the SR and IR are along the_____
orbital axes and the orbital axis is 23 degrees of the visual axis.
pair of muscle in the same eye that move the eye in
opposite directions.
Agonist-antagonist
Give an example of an agonist-antagonist
The medial rectus is the antagonist to the lateral rectus
Muscles in the same eye that move the eye in the same direction.
Synergist muscles
Give an example of a synergist muscle
The inferior oblique and the superior rectus (both go up)
A pair of muscle, one in each eye, that produce conjugate eye movements (moves the eyes in the same direction).
Ex: RLR—LMR
Ex: RIO—LSR
Yoke muscle
Increased innervation (and contraction) to one muscle is accompanied by a reciprocal decreased innervation to its antagonist in the same eye
Sherrington law of reciprocal innervation
Increased innervation to the left medial rectus to contract makes the left lateral rectus relax is an example of
Sherrington law of reciprocal innervation
RMR has increased innervation while RLR does not is an example of?
Sherrington law of reciprocal innervation
In left head tilt, RIO & RIR have innervation to EXTORT while RSO & RSR (to intort) do not. LSO &LSR have innervation to INTORT OS while LIO &LIR do not is an example of
Sherrington law of reciprocal innervation
during conjugate eye movements, equal and simultaneous innervations flow to yoked muscles.
Hering law of equal innervation
When there is a palsy to a muscle, you will notice that the yoke muscle in the other eye will overact. What is this an example of?
Hering law
What is this an example of, RMR has increased innervation and LLR has increased innervation.
Hering law
What is this an example of, On left head tilt, RIO &RIR have increased innervation to excyclotort the right eye and LSO &LSR have the same innervation to incyclotort the left eye.
Hering law
During vertical and oblique versions, what stabilizes the line of sight and prevent horizontal movements?
Horizontal rectus muscles
When the unaffected eye is fixating
Primary deviation
When the paretic or restricted eye is fixating.
Secondary deviation
Why is a secondary deviation larger than a primary deviation?
Because there is an increased innervation to move the paretic eye to fixation.
increased innervation also goes to the non-fixating eye which causes an excessive action and a larger deviation.
What happens during a left lateral rectus palsy if the right eye is fixating?
What type of deviation is this?
the left eye turns in because of the unopposed action of the antagonist (left medial rectus). This is Sherrington law!
This misalignment is a primary deviation.
What happens during a left lateral rectus palsy if the left eye is fixating?
What type of deviation is this?
additional innervation flows to the LLR to establish this. But, an equal increased innervation also flows to the RMR because of Hering law producing an excessive adduction of the OD
Secondary deviation
What is the best position to see the action of the superior oblique?
Depressed and adducted
What is the best position to see the action of the inferior oblique?
Elevation and adduction
What is the best position to see the action of the superior rectus?
Elevated and abducted
What is the best position to see the action of the inferior rectus?
Depressed and abducted
If you told someone to look up and to the right but their OD is still in the primary position what muscle is affected?
Superior rectus is damaged
If you told someone to look up and to the left but their OD is still in the primary position what muscle is affected?
Inferior oblique
If you told someone to look down and to the right but their OS is still in the primary position what muscle is affected?
Superior oblique
If you told someone to look down and to the right but their OD is still in the primary position what muscle is affected?
Inferior rectus
