Ocular motility/Binocular Vision Flashcards
What do the X, Y, and Z signify in Listings plane?
X - horizontal axis
Y - (is not upward, it is coming out of the plane of the paper!)
Z - vertical meridian
Rotation about the X axis correlates which what kind of movement?
Elevation and Depression
Rotation about the Y axis correlates which what kind of movement?
Torsion movement
Note about cyclo ductions/rotations: they are referenced from the top of the eye. So incyclorotations is the top of the eye rotating IN but remember that this means that the bottom is rotating out.
Rotation about the Z axis correlates which what kind of movement?
Abduction and ADDuction
T or F: ductions are binocular
False, they are monocular movements.
What is a version? (conjugate movements)
Eyes moving in the same direction, binocular movements. (i.e extroversion, levoversion)
What are vergences?
Eyes going in opposite directions, binocular movements
(convergence and divergence)
*vergences have the slowest velocity.
LATERAL RECTUS
- What is the primary action
- Where does it insert
- Abduction
- Lateral aspect of the eye
MEDIAL RECTUS
- What is the primary action
- Where does it insert
- ADDuction
- Anterior to the equator
SUPERIOR RECTUS
- What is the primary action
- Where does it insert
- What degree do we have to move it to isolate its action
- Elevation, Incyclorotation, Adduction
- Anterior to equator
- 23 degrees AbDuction
*For SR, IR, SO, IO, the direction of mvmt used to isolate the muscle is OPPOSITE the direction of horizontal mvmt.
*SR ADDucts, therefore we ABduct it to isolate.
NFERIOR RECTUS
- What is the primary action
- Where does it insert
- What degree do we have to move it to isolate its action
- Depression, Excyclorotation, Adduction
- Anterior to equator
- 23 degrees ABduction
*IR ADDucts, so we ABduct to isolate it
SUPERIOR OBLIQUE
- What is the primary action
- Where does it insert
- What degree do we have to move it to isolate its action
- Incyclorotation, Depression, Abduct
- Posterior to equator
- 51 degrees ADDuction
*SO Abducts, so we ADDuct it to isolate. (O’s to the nose)
INFERIOR OBLIQUE
- What is the primary action
- Where does it insert
- What degree do we have to move it to isolate its action
- Excyclorotation, Elevation, Abduction
- Posterior to equator
- 51 degrees ADDuction
*IO Abducts, so we ADDuct it to isolate. (O’s to the nose)
Spiral of Tillaux
Which muscle has the closest attachment site to the front of the eye?`
MILS
Medial rectus (5.5)-> Inferior rectus -> Lateral Rectus -> Superior Rectus (7.77)
What is Donder’s Law?
For any position of gaze, the eye has a unique orientation in 3D space. The path taken doesn’t influence orientation.
What is Listing’s law?
The eye must rotate around axes to achieve a position of gaze.
What is Hering’s law?
hEring = Equal innveration
Yoked muscles (one from each eye) must recieve equal innervation
What is Sherrington’s law?
[bicept/tricept law] Agonist and antagonist EOMs of the SAME eye are reciprocally innervated.
“excited and inhibited pair”
There are two reason’s why the eye moves?
- To get image on the fovea
- To keep the image on the fovea
What is the troxler effect?
Fading of peripheral images when the eye is fixated on a central object. The small, involuntary movements that occur during fixation help to minimize this effect.
What is the difference between micro saccades, micro tremors, and microdrifts?
- Microsaccades:
-intentional conjugate eye mvmts (move image back onto fovea)
-Counteract errors in monocular fixation produced by spurious micro drifts and microtremors - Microtremors:
-unintentional dysconjugate eye mvmts
-have high frequency - Microdrifts:
-unintentional dysconjugate eye mvmts
-large and slow
What are the 4 key points to keep in mind about the vestibulo-ocular reflex? (VOR)
- Stabilizes images on the fovea during HEAD MVMTS by producing an eye mvmt of equal MAGNITUDE in the opposite direction.
- ENDOLYMPH in the semicircular canals
- for FAST eye movement
- for ACCELERATION (reflex fades after 30 seconds of duration).
-not used for constant motion.
job is to keep image on fovea
How can you test the Vesibular system to ensure VOR is working?
- Have pt rotate their head & ensure their eyes rotate the opposite way to maintain fixation
- Choloric testing, pour water in one ear.
Is the direction of mvmt named for the slow or fast phase of eye movement?
Fast phase!
This is tricky because the first movement is the slow phase and then fast phase is second and we name it for the fast phase.
What direction should the eyes move if you put cold water in one ear?
“COWS”
Cold -> opposite. Eyes will make a slow phase toward the ear and then a FAST phase AWAY.
T or F: optokinetic system is used for acceleration.
False.
It is used for constant motion.
-Optokinetic reflex is what kicks in after the vestibular system has been going for 30 sec stops off.
What is the difference between Optokinetic Reflex and Optokinetic Nystagmus?
- Optokinetic reflex: what kicks in after the vestibular system stops. For constant head motion w/ a fixed target.
- Optokinetic Nystagmus: head is still but target is moving at a constant speed (OKN drum)
“reflex, you are moving. nystagmus, your target is moving”
When do we typically use the OKN drum?
Used when you don’t know if a pt can see or not. i.e. stroke pt or baby. If their eye flicker, we know they could see it.
+ positive OKN means pt can see that acuity or better.
- a neg response is inconclusive, decreased VA and/or a parietal lobe lesion.
compare and contrast oscillopia and vertigo
Oscillopia: Sensation of objects move up and down in the visual field. -World is moving–
Vertigo: Sensation that body is moving around in the environment even though it is still. –Body is moving–
What is Jerk nystagmus?
-has a slow and fast phase
-The slow phase represents and abnormality in fixation
-The fast phase is the correcting saccade to bring the fovea back on the target.
-Named for fast phase
What is pendular nystagmus?
Even back and forth mvmt of the eyes like a grandfather clock.
What is a null point?
The direction of gaze where the nystagmus has the lowest amplitude.
Congenital (infantile) nystgmus is a pathologic nystagmus that is present at birth or before age 6.
What conditions is it associated with? (6)
Males 2x
-Aniridia
-albinism
-achromatopsia
-optic nerve hypoplasia
-optic atrophy
-congenital cataracts
all things that decrease vision at a young age
Latent nystagmus is pathologic as well.
What does it look like?
-unilateral
-Comes up while doing cover test, when one eye is covered, the other shakes.
-associated with infantile esotropia (almost always) and amblyopia.
Spasmus nutans is another type of pathologic nystagmus, what is it characterized by?
Triad:
1. Nystagmus
2. Head nodding
3. Abnormal head position
-Resolves after 2-8 years.
What is convergence-retraction nystagmus?
*Co-contraction of EOM on attempted up gaze
*Happens when ask patient to make upward gaze or follow downward OKN drum
*Other features: paresis of up gaze, light near pupil dissociation, bilateral lid retraction
What is Gaze-evoked nystagmus
*Inability to maintain fixation in eccentric gaze
*Jerk nystagmus in direction of eccentric gaze
*Amplitude increases when eyes are moved in the direction of the fast phase
-can be due to drugs.
What is See-saw nystagmus?
- One eye: elevation & intorsion (up & in)
- Other eye: depression & extortion (down and out)
*Reverses during next half cycle
*Pendular or jerk
*if pendular: Bitemporal VF (due to lack of crossing fibers)
What is the very general difference between a saccade and a pursuit?
- Saccades: following something that is NOT moving.
- Pursuit: following something that IS MOVING
