Ocular Motility Flashcards
Listing’s Plane
What are the 3 axes
Z is vertical
X is horizontal
Y is coming out at me
Rotation about Z and X are in secondary positions of gaze.
Tertiary positions of gaze involve looking in an oblique direction.
Tangential point
The point where the muscle tendon first makes contact with the globe of the eye
Arc of contact
The area between the tangential point (the point where the muscle tendon first makes contact with the globe) and the point of insertion of the muscle on the globe and exerts it’s action.
Ductions
Mono or bino?
Mono
Versions
Conjugate movements.
Both eyes moving in the same direction
Dextro (right) and Levo (left)
When making a cyclo movement, it is a rotation about the y axis such that the ____ portion of the eye tilts in or out.
UPPER
Where does the SR insert in reference to the equator and at which degree to primary gaze
anterior temporal to the equator
23
Where does the IR insert in reference to the equator and at which degree to primary gaze
Anterior Temporal
23
Where does the SO insert in reference to the equator and at which degree to primary gaze
Posterior medial
54
Where does the IO insert in reference to the equator and at which degree to primary gaze
Posterior medial
51
How to remember that obliques insert posterior medial to the equator
Obliques are sleepy (PM) after they finished working on their abs
How to isolate the recti muscles of right eye
Look temporally 23 degrees
How to isolate the oblique muscles
O’s to the nose
Look medially 54/51 degrees
Spiral of tillaux
Describes the line of insertion of the RECTI muscles on the globe.
MR inserts closest to the limbus –> IR –> LR –> SR inserts furthest from the limbus.
Therefore, the MR has the most anterior insertion site and has the strongest effect on the globe when it contracts.
Donder’s Law
For any position of gaze, the eye has a unique orientation in 3 dimensions of space. The orientation of the eye for a particular gaze is always the same, regardless of where the eye was initially positioned before moving to that gaze.
Listing’s Law
The eye rotates around axes (X, Y, and Z)
Hering’s law of equal innervation
Synergistic muscles/yoke muscles of the 2 eyes receive equal innervation in order for the eyes to produce smooth movements.
Sherrington’s law
Agonists and antagonists of the same eye are reciprocally innervated. When the agnostic is excited, the antagonist is inhibited.
Eye movements serve 2 primary purposes
- Move the eye so that the fovea aligns with an object of interest
- Hold images in place on the retina.
Which structure is responsible for initiating VOR?
Semi-circular canals
Stimuluated by movement of endolymph within the semicircular canals of the ear that occur during head movement
The VOR does not require a visual stimulus. It will occur in response to head movement even if the eyes are closed.
3 eye movements associated with steady fixation
- Microsaccades. Intentional conjugate movements. Move the fovea back on an object of interest after micro drifts and micro tremors.
- Microtremor- unintentional, disconjugate eye movement. result of neural noise in the brainstem.
- Microdrifts- unintentional, disconjugate eye movement. Larger and slower than micro tremors. result of neural noise in the brainstem.
Stabilizes images on the fovea during brief head movements by producing an eye movement of equal mag to the head movement in the opposite direction.
VOR
VOR
- fast or slow?
- Short or long latency?
Rapid (300 degree/sec) and small latency (15 msec)
When does VOR stop working? What takes over?
VOR reflexes begin to fade with sustained head movements over 30 seconds in duration. The optokinetic reflex system is then responsible for continuing the eye movements.
Which reflexes take place when the head is still vs moving?
Head still- OKN
Head moving-
short term is VOR
Long term is optokinetic reflex
damage to the vestibular system can result in
Horizontal nystagmus
Central lesions are accompanied by other neuro symptoms such as nausea, oscillopsia, vertigo.
Difference between oscillopsia and vertigo
oscillopsia: Sensation of objects moving up and down.
vertigo: Sensation of the body moving around the environment even though it is still.
3 ways to test for vestibular dysfunction.
- Dolls head movement (Oculocephalic)
- Caloric testing. COWS (named for the fast phase)
- Rotational testing- spin patient in chair. Slow movement in direction of rotation, fast in opposite.
Diff between null and neutral point
Null- Nystagmus has lowest amplitude
Neutral- Direction of gaze where nystagmus changes direction.
Difference between physiologic and pathologic nystagmus
Physiologic- Often conjugate jerk nystagmus without associated symptoms or decreased vision
Pathologic- Dissociated (disconjugate) eye movements with excessive drift, causing decreased VA and oscillopsia.
End point nystagmus vs gaze evoked nystagmus
End point- Small conj jerk nystagmus in extreme gaze. Worse when sleepy.
Gaze evoked- Occurs in the presence of other motor abnormalities. Maybe trouble fixating or pursuits.
Congenital infantile nystagmus
- More common in which gender
- What conditions may cause this
Nystagmus present at birth or before age of 6.
Horizontal and conjugate
Males x 2 > females
40% afferent, 60% efferent defects.
Anirida, albinism, chromatopsia, optic nerve hypoplasia, congenital cataracts.
Latent nystagmus
-Commonly associated with ____
Congenital, conjugate jerk nystagmus that increases in velocity and amp when one eye is occluded.
Commonly associated with essential infantile esotropia and amblyopia.
Spasmus Nutans
Nystagmus that develops shortly after birth and then resolves at 2-8 years.
pendular nystagmus, head nodding and head turns.
Convergence retraction syndrome
- Occurs when looking in what direction
- Associated with __ syndrome
Occurs when patient looks up.
The eyes will move slowly down (slow phase) followed by a fast phase causing convergence and retraction.
Associated with dorsal midbrain syndrome.
See-saw nystagmus
Elevation and intorsion of one eye, depression and extortion of other.
Seen in pituitary tumors.
____ maintains a stable image of a moving object on the fovea when the head is still.
OKN
What results because the cortical regions of the brain responsible for the OKN response are not fully developed at birth
Pt can have OKN response temporal to nasal, but not nasal to temporal.
If patient does not have OKN response, consider
Decreased VA or parietal lobe lesion.
Main difference between pursuits and saccades
Saccades look at stationary objects.
Pursuits track moving objects.
Characteristics of saccades
- Rapid and yoked
- Invol and voluntary
- Fast velocity, slow latency
- Once started, cannot change
- Damage to right FEF? Cannot make saccade to the left.
- Saccadic suppression occurs to prevent blurring during the saccade.
- Abnormalities with saccades= poor reading.
saccades are controlled by __ __
Pursuits are controlled by __ ___
Saccades controlled by contra FEF
Pursuits controlled by ipsi partial lobe
Ocular flutter and opsoclonus
Ocular flutter- Multiple, spontaneous, conjugate horizontal saccades that decrease in amplitude over time.
opsoclonus- Advanced form of ocular flutter.
*Associated with cerebellar disease. MG, Parkinson’s, alzheimers, INO.
Characteristics of pursuits
Slow, tracking movements that allow continuous fixations
Tracks a moving object
Voluntary only
Controlled by ipsi parietal lobe
Leads to poor performance in sports
Cogwheeling
A series of step like eye movements that are used to follow a moving object, rather than a smooth pursuit
Accommodative convergence is initiated by
Blur
Comitant vs Noncomitant deviation
Comitant- A misalignment of the visual axis of each eye that is the same in all positions of gaze. Indicates a decompensated phoria. No further testing required.
Non-comitant- A misalignment of the visual axis of each eye that is not the same for all positions of gaze. Indicates an anatomical muscle restriction and muscle palsy. Do forced ductions to differentiate between a (+) restriction or (-) palsy. If muscle palsy, do parks 3 step to determine muscle involved if there is a vertical component
In a patient with an abnormal head turn secondary to a non-comitant deviation, which way will the face point?
In the direction that corresponds to the field of action of the affected muscle.
*Head tilt is more variable. If SO palsy, head will tilt away. if IO palsy, head will tilt towards
Why will the magnitude of a non-comitant deviation vary depending on which eye is used for fixation?
Primary deviation- Deviation of the paretic eye when normal eye is fixating
Secondary- Deviation of the normal eye when paretic eye is fixating
Secondary deviation will always be greater due to herring’s law of equal innervation. Greater stimulus is necessary to maintain fixation of the paretic eye, resulting in a greater stimulus to the yoked muscle in the normal eye and larger deviation.
4 subjective tests for comitancy
Red lens testing - the patient puts a red lens in front of one eye and looks at pen light. The patient t describes the relative positions in 9 directions of gaze.
Hess-Lancaster test- Pt wears red green glasses and views a grid. Can measure primary and secondary deviations by switching around the red-green glasses.
CT
Maddox Rod
+ and - meanings on forced duction test
Think that the goal is to find a muscle restriction
(+) Muscle restriction. Think graves, orbital tumor, entrapment of muscle.
(-) Palsy
Duane’s Retraction Syndrome and the 3 types
Congenital
CN III innervates both the MR and LR
Type 1: Limited Abduction (1 D)
Type 2: Limited Adduction (2 D’s)
Type 3: Limited aduction and adduction (3 D’s)
When patient adducts, the eye will retract back into the globe and the palpebral fissure will narrow.
Brown’s Syndrome (SO tendon sheath syndrome)
BROWN is down!
Can be acquired or congenital.
Abnormality of the SO muscle and tendon or abnormality of the trochlea.
Hypotropia in primary gaze and limited elevation during Adduction (when SO is isolated)
