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Ocular Motility > Sections 1 - 4 > Flashcards

Sections 1 - 4 Flashcards

1
Q

Listing’s Plane

A
  • plane normal to the visual axis passing through the equator of the globe and the center of rotation of the eye when it is in the primary position of gaze
  • x: vertical (secondary position)
  • y: torsional (secondary position)
  • z: horizontal (secondary position)
  • tertiary: looking oblique
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2
Q

Muscle Plane

A
  • the plane that describes the direction of pull of an individual EOM
  • passes through the center of rotation of the eye
  • determined by the origin and insertion site of EOM
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3
Q

axis of rotation

A
  • the axis perpendicular to the muscle plane
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4
Q

tangential point

A

the point where the muscle tendon first makes contact with the globe of the eye

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5
Q

arc of contact

A

the area between the tangential point and the point of insertion of the muscle on the globe of the eye; the area where the muscle exerts its action on the eye

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6
Q

duction is a __________ rotation

A

monocular

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7
Q

cyclo is named for the ______ portion of the eye

A

upper

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8
Q
  • versions are _______ eye movements
  • what is the purpose of versional (conjugate) eye movements?
A
  • binocular
  • enlarge the field of view and to move the fovea of each eye to an object of fixation; may be voluntary or involuntary
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9
Q

dextroversion vs. levoversion

A

dextroversion: z-axis; right
levoversion: z-axis; left

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10
Q

dextrocycloversion vs. levocycloversion

A

dextrocycloversion: y-axis; right
levocycloversion: y-axis; left

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11
Q

define vergence

A
  • align visual axes of both eyes to obtain binocular fixation and fusion
  • disconjugate eye movements (move in opposite directions)
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12
Q

how do you isolate SR muscle?

A

have patient turn eye out towards ear 23 degrees away from the line of sight

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13
Q

how do you isolate the oblique muscles?

A

have the patient look towards their nose

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14
Q

primary/ secondary/ tertiary actions
MR:
LR:
SR:
IR:
SO:
IO:

A

MR: adduction
LR: abduction
SR: elevation, intorsion, adduction
IR: depression, extorsion, adduction
SO: intorsion, depression, abduction
IO: extorsion, elevation, abduction

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15
Q

SR: inserts on the ____ of the eye _______ to the equator and _____ degrees temporal to the line of sight

A

top, anterior, 23

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16
Q

IR: inserts on the ______ of the eye _______ to the equator and _____ degrees temporal to the line of sight

A

bottom, anterior, 23

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17
Q

SO: passes through the ______ and travels diagonally to insert on the upper temporal region of the eye, _______ to the equator, ______ degrees medial to the line of sight

A

trochlea, posterior, 54

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18
Q

IO: inserts on the lower temporal region of the eye, ______ to the equator at angle ______ degrees medial to the line of site

A

posterior, 51

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19
Q

spiral of tillaux

A

describes the line of insertion of the recti muscles on the globe of the eye

MR: closest to the limbus
SR: furthest away from the limbus

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20
Q

why does the MR have the strongest effect on the globe when it contracts?

A

because it has the most anterior insertion

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21
Q

what 2 muscles are isolated for vertical eye movements when the eye is rotated 23 degrees away from the nose?

A

SR, IR

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22
Q

what law states that yoked eye muscles between the eyes receive equal innervation?

A

hering’s

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23
Q

define donder’s law.

A
  • for any position of gaze, the eye has a unique orientation in 3D 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
  • the starting location of the eye and the path taken to a unique position of gaze do not influence the orientation of the eye at the final position of gaze
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24
Q

define listing’s law

A

the eye mist rotate around axes to achieve a given direction of gaze

these axes are located in a single plane called listing’s plane

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25
Q

list yoke muscle pairs (one muscle per eye)

A

LR & MR
SR & IO
SO & IR

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26
Q

define sherrington’s law

A
  • two muscles of the same eye
  • agonist and antagonist EOMs of the same eye are reciprocally innervated
  • SR & IR
  • IO & SO
  • LR & MR
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27
Q

eye movements serve two primary purposes: 2

A
  1. move the eye so that the fovea aligns with an object of interest
  2. hold images in place on the retina
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28
Q
  1. move the eye so that the fovea aligns with an object of interest
    - what does the saccade system do?
    - what does the smooth pursuit system do?
    - what does the vergence system do?
A
  • the saccade system moves the eye very rapidly to align the fovea with an object quickly
  • the smooth pursuit system moves the eye at the same speed as a moving target to keep the target on the fovea
  • the vergence system aligns the eyes through convergence/divergence to ensure bifoveal fixation of an object in order to maintain fusion and binocular vision
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29
Q
  1. hold images in place on the retina
    - the fixation system holds an image on the fovea while the head is _________
    - the vestibular system (____) holds an image on the fovea during ______ motions of the head
    - the optokinetic system holds an image on the fovea during ______ head movements
A
  • motionless
  • VOR, short
  • prolonged
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30
Q

t/f: the eye is constantly moving during fixation

A

true

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31
Q

involuntary eye movements continuously shift an image onto neighboring ________, preventing what?

what effect does this minimize?

A
  • photoreceptors
  • bleaching of the retina, fatigue, and subsequent fading or smearing of an image
  • Troxler
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32
Q

define microsaccades

A
  • intentional conjugate eye movements
  • mod. high velocity (2-10 degrees/sec)
  • amplitude (6 arc minutes)
  • move the fovea back on an object of interest after microdrifts and microtremors
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33
Q

define microtremors

A
  • unintentional disconjugate eye movements
  • high frequency (65-75 Hz)
  • amplitudes (10 arc minutes)
  • fastest of the 3 types of eye movements associated with fixation
  • the result of neural noises within the brainstem
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34
Q

define microdrifts

A
  • unintentional disconjugate eye movements
  • larger and slower
  • velocity: 1 arcminute/sec
  • amplitude: 6 arc minutes
  • neural noise in the brainstem
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35
Q

t/f: microsaccades counteract errors in monocular fixation produced by spurious microdrifts and microtremors

A

true

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36
Q

what drives the VOR system?

A

ears (vestibular)

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37
Q

VOR: 4 key points

A
  1. stabilize the image on the fovea; brief head movement; opposite direction
  2. stimulated by endolymph
  3. fast eye movements
  4. optokinetic system kicks in after 30 seconds of sustained head movement
38
Q

t/f: VOR does not require a visual stimulus and occurs even if eyes are closed

A

true

39
Q

VOR occurs very rapidly (_____ degrees/ second) and very small latency (___ msec)

A

300
15

40
Q

a patient has a problem w/ endolymph =

A

horizontal nystagmus issue (acute lesion)

41
Q

central vestibular lesions (vestibular nuclei in the brain or vestibular connections to the brainstem/ cerebellum) are commonly accompanied by what?

damage to the inner ear is often accompanied by: 3

A

other neurological symptoms

nausea, oscillopsia, vertigo

42
Q

define oscillopsia

A

the sensation of objects moving up and down in the VF

  • vertigo is the sensation that the body is moving around the environment even though it is still
43
Q

define oculocephalic testing

A
  • doll’s head maneuver
  • pt. is asked to fixate on a distant target while the head is moved from side to side or up and down
  • normal: conjugate eye movements in opposite direction as head movement
44
Q

define caloric testing

A
  • pt. positioned so the head is elevated 30 degrees
  • head is turned to the side, and water is slowly poured into the inner ear
  • intact vestibular system:
    warm water in the right ear = slow conjugate movement to the left, which leads to a resulting fast movement back towards the right (caloric nystagmus)

cold water poured into the right ear will result in nystagmus with a fast phase to the left

COWS

45
Q

define rotational testing

A
  • pt. slowly rotated in a chair for ~ 20 seconds
  • normal: slow conjugate eye movements in the direction of rotation, followed by fast eye movement in the opposite direction
46
Q

define nystagmus

A
  • involuntary back and forth movement of one or both eyes that disrupts fixation (H, V, T in direction)
  • 2/2 pathology of the afferent visual pathway, disruption of ocular motor control, or due to abnormalities of the eye movements for stable fixation
47
Q

define jerk nystagmus

A
  • characterized by slow and fast phase
  • named for the direction of fast or corrective phase
48
Q

null point vs. neutral point

A

null: lowest amplitude
neutral: changes direction

49
Q

physiologic nystagmus is often a _______ ________ nystagmus w/o associated symptoms or decreased vision

A

conjugate jerk

50
Q

how is pathologic nystagmus characterized?

A
  • disconjugate eye movements with excessive drift
  • decreased va
  • oscillopsia
51
Q

define endpoint nystagmus

A
  • small, intermittent
  • conjugate jerk
  • extreme horizontal positions of gaze
  • worse when the patient is tired
52
Q

define optokinetic nystagmus

A
  • conjugate jerk
  • responsible for maintaining the image of a moving object on the fovea when the head is stationary
53
Q

define caloric and rotational nystagmus

A

caloric: conjugate jerk produced during caloric testing

rotational: conjugate jerk produced in response to head/body rotation

54
Q

define congenital (infantile) nystagmus

A
  • present at birth before age 6
  • M>F (2x M)
  • horizontal, conjugate
  • pendular or jerk
  • 40% due to defects in the afferent pathway
  • results in poor image formation on the fovea and inadequate feedback to the oculomotor system to control fixation
  • 60% due to efferent lesions
55
Q

conditions that lead to poor image formation and the fovea with subsequent nystagmus

A
  • aniridia
  • albinism
  • achromatopsia
  • optic nerve hypoplasia
  • optic atrophy
  • congenital catatacts
56
Q

define latent nystagmus

A
  • congenital
  • conjugate jerk
  • increases in velocity and amplitude when one eye is occluded (cover test)
  • horizontal (fast phase towards fixating eye)
  • commonly associated with essential infantile esotropia and amblyopia
57
Q

define spasmus nutans

A
  • develops within 4-12 months after birth
  • resolves after 2-8 years
  • family history, no sex predilection
  • disconjugate
  • high frequency
  • low amplitude
  • pendular
  • H & V components
  • accompanied by compensatory head nodding, and ~ 50% of pts have a head turn
58
Q

define convergence retraction syndrome

A
  • intermittent jerk w/ fast phase
  • upgaze: eyes move slowly down (slow phase) followed by fast phase causing convergence and or retraction (replacing quick movement toward upgaze)
  • dorsal midbrain syndrome
59
Q

define gaze-evoked nystagmus

A
  • jerk
  • extreme gazes (H or upgaze)
  • conjugate or disconjugate
  • occurs in the presence of ocular motor abnormalities
  • 2/2 drug use (alcohol, sedatives, anti-convulsants) or posterior fossa disease
60
Q

define see-saw nystagmus

A
  • elevation and intorsion of one eye and depression and extortion of the fellow eye in a pendular or jerk waveform
  • parasellar lesions (pituitary tumor)
  • maybe congenital in nature
61
Q

t/f: always evaluate binocular vision, the OKN response, VOR response, saccades, and pursuits to differentiate between pathological and physiological

A

true

62
Q

OKN has a ______latency than VOR response

A

longer

63
Q

the ___________ reflex is responsible for maintaining an image on the fovea with prolonged head movements (> 30-sec duration) after VOR responses start to fade

A

optokinetic

64
Q

____________ nystagmus maintains the image of a moving object in the fovea when the head is still

A

optokinetic

65
Q

the _______ regions of the brain are responsible for the OKN response - but they are not fully developed at birth; this results in what?

A
  • cortical
  • nasal to temporal optokinetic nystagmus is absent in infants until 3-4 months of age
66
Q

an OKN drum when rotated slowly and watched by pt., optokinetic nystagmus will occur with the ____ phase in the direction of the rotation of the drum

A

slow

67
Q

t/f: OKN drum can be used as a gross method of measuring VA in infants

A

true

68
Q

what does a positive OKN response denote?
negative?

A

+: VA equal to or better than the corresponding VA size of the drum stripes
-: inconclusive, decreased VA and/or a parietal lobe lesion should be considered

69
Q

saccades: 7 key points

A
  1. very rapid, yoked eye movements
  2. most are voluntary, certain stimuli can elicit involuntary saccades
  3. fast velocity, slow latency (it takes a while for the brain to decide to start a saccade)
  4. once started, can’t change the amplitude (the most common saccadic error is an undershoot)
  5. contralateral FEF
  6. to prevent blurring during a saccade, vision is suppressed by the cortex (saccadic suppression)
  7. abnormalities (think would this cause poor reading)
70
Q

define microsaccades

A

similar amplitude and velocity, used for reading (5x/min)

71
Q

damage to the right FEF results in impaired saccades toward the _______ (_______ to the lesion)

resulting in the eyes turning to the ______ (_______ the lesion)

effects are usually temporary and disappear within weeks

damage to _______ ________ causes a change in the velocity and accuracy of saccades; transient

A

left, opposite
right, towards
superior colliculus

72
Q

review DEM, NSUCO, king devick

A

review DEM, NSUCO, king devick

73
Q

what is readalyzer?

A
  • objective test
  • assess comprehension and reading ability (saccades)
  • score below 15th percentiles = saccadic dysfunction
  • similar to visagraph
74
Q

name and define 3 inappropriate saccades

A
  • square-wave jerk: rare, uncontrollable, random, macro square, larger than 10 degrees
  • ocular flutter: multiple, spontaneous, conjugate, horizontal, spring-like, decrease in amplitude over time, occur after a series of small saccades or during fixation
  • opsoclonus: advanced ocular flutter, almost constant, involuntary conjugate saccades in multiple directions, occur only while awake
75
Q

ocular flutter and opsoclonus are typically associated with __________ disease

name 5 other disorders characterized by abnormal saccades

A

cerebellar

MG, Parkinson’s, ocular motor apraxia, PSP, INO

76
Q

4 key points: pursuits

A
  1. slow, tracking, continuous fixation, on a moving target
  2. latency ~ 125 msec, velocity 50 degrees/second
  3. parietal lobe, ipsiliateral side
  4. abnormalities - trouble in sports
77
Q

vergence
- latency:
- velocity:

A
  • latency: 160 msec
  • velocity: 10 degrees/sec
78
Q

define tonic vergence

A
  • @ rest at distance w/o stimulus to converge or accommodation
  • clinically measured as the best-corrected distant phoria
79
Q

define fusional vergence

A
  • initiated by retinal disparity and helps eyes compensate for a phoria to obtain bifoveal fixation or binocular vision
  • motor fusion
80
Q

accommodation and convergence are linked to one another in a way characterized by ____

A

AC/A ratio

81
Q

near reflex triad

A

convergence
accommodation
miosis

82
Q

define decompensated phoria

A
  • large phoria that a patient has usually been able to compensate for but is now unable to do so
  • results in tropia or symptoms of diplopia
83
Q

comitant vs. non-comitant deviation

A

comitant deviation: misalignment of the visual axis of each eye that is the same in all positions of gaze (decompensated phoria)

non-comitant deviation: misalignment of the visual axis of each eye that is not the same in all positions of gaze (indicated anatomical muscle restriction or a muscle palsy)

84
Q

if the deviation is non-comitant, _______ ________ should be preformed to differentiate between restriction vs palsy

A

forced duction

85
Q

if the patient has a non-comitant deviation, the deviation will be worse when looking in the direction of the ___________ muscle

example: CN6 (affecting SO) is characterized by a hyper deviation that increases with ________ and _________ of the affected eye

A

underperforming
adduction
depression

86
Q

head tilt away from the side of the lesion: _____
head tilt towards the side of the lesion: _____

A

SO
IO

87
Q

primary deviation: deviation of the paretic eye when normal eye is ________

A

fixating

88
Q

t/f: secondary deviation will always be greater than primary deviation

A

true
because of herings law

89
Q

a pt. w/ a (L) SO palsy will have the greatest diplopia when looking in what direction?

A

down and to the right

90
Q

review red lens test, hess-lancaster, forced duction

A

review red lens test, hess-lancaster, forced duction

91
Q

Duane’s (1-3); CN 3 innervates MR and LR (LR is usually innervated by CN6)

results in:

A
  • globe retraction
  • narrow palpebral fissure in adduction (due to violatin of sherringtons law
  • estropia primary gaze
92
Q

define browns syndrome

A
  • SO tendon sheath syndrome
  • acquired (iatrogenic damage, scarring or inflammation of the trochlea)
  • congenital (SO is too short or tendon is too elastic)
  • unilateral
  • small hypotropia in primary gaze
  • limited elevation during adduction
  • ddx: IO paralysis, overaction SO, orbital for fracture

Ocular Motility (1 decks)

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