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Ocular Motility > Definitions/EOMs > Flashcards

Definitions/EOMs Flashcards

1
Q

Why is ocular movement assessed?

A
  • Establish the extent of mov’t of the globe

- prove the integrity of the diff mov’t systems/nervous system pathways

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2
Q

Tangential Point

A

Point at which the center of the muscle or of its tendon first touches the globe

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3
Q

Muscle Plane

A

The tangent to the globe at the tangential point and the center of rotation

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4
Q

Axis of Rotation (AOR)

A

Perpendicular to the muscle plane erected in the center of rotation corresponds to each muscle plane

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5
Q

Arc of Contact

A

Arc formed b/t the tangential point and the center of insertion of the muscle on the sclera, the area where the muscle exerts its action

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6
Q

Angle Kappa

A
  • Angle formed by intersection of the pupillary axis and visual axis
  • Caused by failure of the optical and visual axes of the eye to coincide
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7
Q

Pupillary axis

A

Line passing through the center of the pupil perpendicular to the cornea

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8
Q

Optical axis

A

Line connecting the optical centers of the cornea and the lens

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9
Q

Visual axis

A

AKA line of sight, connects the fovea with the fixation point

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10
Q

Positive angle kappa

A
  • Fovea lies temporal to the posterior pole and reflection = nasal
  • Referred to as pseudo exotropia
  • This is normal (avg = 5.082 degrees)
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11
Q

Negative angle kappa

A

This is unusual
Fovea lies nasal to the posterior pole and reflection is temporal
Referred to as pseudoesotropia

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12
Q

Angle alpha

A

Angle b/t the optical ax’s and the visual axis = nodal point/angle alpha

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13
Q

Angle gamma

A

Angle between the optical axis and fixation axis referred to the center of rotation

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14
Q

What is the only angle that can be clinically measured of the ones we discussed?

A

Angle kappa

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15
Q

Where does the optical axis (AB) touch the posterior pole?

A

Slightly nasal and inferior to the fovea

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16
Q

What are conjugate movements?

A

Movements of the eye in the same direction at the same time

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17
Q

What are versions?

A

Binocular rotations of the eyes in qualitatively the same direction (aka conjugate movements)

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18
Q

What is dextroversion?

A

Both eyes rotating about the z axis to the right

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19
Q

Levoversion

A

Both eyes rotating about the z axis to the left

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20
Q

Dextrocycloversion

A

Rotations about the y axis such that the upper portion of both eyes tilt to the patient’s right

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21
Q

Levocycloversion

A

Rotations about the y axis such that the upper portion of both eyes tilt to the patient’s left

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22
Q

Disconjugate

A

Movements of the two eyes in opposite directions to see objects singly at different distances from us aka vergences

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23
Q

Vergences

A

Aka disjunctive mov’ts; movement of the 2 eyes in opposite directions

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24
Q

Convergence

A

Eyes turn inward

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25
Q

Vergence

A

Eyes turn outward

26
Q

What is true torsion?

A

Rotation of the eye about its anteroposterior axis

27
Q

Fusion

A

Formation of one image from the two images seen simultaneously by the two eyes

28
Q

Motor fusion

A

Adjustments made by the brain in innervation of extraocular muscles to bring both eyes into bifoveal and torsional alignment

29
Q

How is motor fusion stimulated?

A

Disparity in images received fro, the two eyes such as fixation object moving towards or away from the subject

30
Q

Sensory fusion

A
  • Aka binocular vision, sensory fusion, stereopsis
  • Integration in the visual sensory areas of the brain of images seen with the two eyes into one picture
  • Position of eye is determined by the equilibrium achieved by the pull of all 6 EOMs
31
Q

What is an example of sensory fusion and what stimulates it?

A
  • The waterfall illusion

- Stimulus to sensory fusion is the excitation of the corresponding retinal images

32
Q

Heterophoria

A

Latent deviation of the eyes which are held straight by binocular fusion

33
Q

Heterotrophia

A

Manifest deviation of the eyes

34
Q

Orthophoria

A
  • A sense of any tendency of either eye to deviate when fusion is suspended
  • this is rarely seen clinically (small phoria is normal)
35
Q

Prism diopter

A
  • Unit of angular measurement used to characterize ocular deviations
  • 1 diopter prism reflects ray of light towards base of prism by 1 cm
  • One degree of arc = 1.7 PD approx
36
Q

Primary position of gaze

A

Head and eyes are both aligned w object of regard

37
Q

Secondary position of gaze

A
  • Posterior of the eyes when either a purely horizontal or purely vertical mov’t is made from primary position
  • NO associated tilt of the vertical meridians with respect to objective vertical
38
Q

Tertiary position

A

Position of the eyes when they move from primary position to any other position EXCEPT secondary position

39
Q

False torsion

A
  • The APPARENT cyclorotation of the eye associated with the change in direction of regard from primary position to some tertiary position
  • It is NOT true torsion
40
Q

Antagonist

A

The muscle that resists the pull of the agonist
It must relax for a new direction of gaze to be achieved
Have opposite field of action

41
Q

Agonist

A

The muscle that contracts to pull eye in desired direction

42
Q

Field of action

A

Direction of gaze in which the muscle exert its greatest contraction force as an agonist

43
Q

Synergistic

A

Muscles that have the same field of action

44
Q

Medial Rectus

A

Primary - adduction

45
Q

Lateral rectus

A

Primary-abduction

46
Q

Inferior rectus

A

Primary- Depression (greatest when abducted)
Secondary - Excycloduction (greatest when adducted)
Tertiary - Adduction

47
Q

Superior rectus

A

Primary- Elevation (greatest when abducted)
Secondary - Incyclorotation (greatest when adducted)
Tertiary - Adduction

48
Q

Inferior Oblique

A

Primary - Excycloduction (greatest when abducted)
Secondary - Elevation (greatest when adducted)
Tertiary - Abduction

49
Q

Superior oblique

A

Primary - Incycloduction (greatest when abducted)
Secondary - Depression (greatest when adducted)
Tertiary - Abduction

50
Q

Spiral of Tillaux

A

Insertions of the rectus muscles are not equidistant to corneal limbus they are inserted as a spiral

51
Q

Listing’s plane

A
  • Plane passing they the head and center of rotation of the eye perpendicular to the line of sight when eyes are in primary position
  • x and z lie in this plane
52
Q

Three axes of Fick

A

Mov’t of globe takes place around the three axes of Fick (x,y,z) all passing thru center of rotation

53
Q

Listing’s Law

A

Mov’t of the eye from primary position to any other position is equivalent to a single rotation about an axis in Listing’s plane

54
Q

Donder’s Law

A

Angle of tilt for a given tertiary position of the eye is always the same regardless off the path the eye has used to obtain that position

55
Q

Sherrington’s Law of Reciprocal Innervation

A

When an agonist contracts during mov’t there is a simultaneous and equal relaxation of the antagonist

56
Q

Herring’ s Law of Equal Innervation

A

Yoked muscles are equally innervated and innervation is based of the fixating eye

57
Q

Yoke pair

A
  • For mov’t of both eyes in the same directions, the corresponding agonist muscles wit the same FOA = yoke pair
  • Pair of agonist muscles with same primary action
58
Q

Why is there a difference between the fields of action and diagnostic positions of gaze?

A

Diagnostic positions of gaze are used to ISOLATE a specific muscle to check function
-based upon biomechanics of the eye
Ex.) when eye is fully abducted only IR can depress the eye

59
Q

Concomitant

A
  • Strabismic deviation is equal magnitude in all fields of gaze
  • Deviation not affected by which eye is fixating or direction of gaze
  • Typical in childhood/non-paretic strabismus
60
Q

Incomitant

A
  • Deviation varies according to which eye is fixating and the direction of gaze
  • Typical in recent onset of EOM paresis/acquired strabismus
  • Will cause overaction of the non-affected eye
61
Q

Primary deviation

A

Incomitant deviation measured w normal eye fixating

62
Q

Secondary deviation

A

Incomitant deviation measured with affected eye fixating

Ocular Motility (1 decks)

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