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Binocular Vision > (G1) Anatomy & Physiology of the Motor Mechanism > Flashcards

(G1) Anatomy & Physiology of the Motor Mechanism Flashcards

1
Q

The visual axis passes through the nodal point and the fovea centralis, thus crossing the optic axis making a small angle, commonly spoken as?

A

Angle Gamma

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2
Q

Clinically this angle is assessed at the pupillary plane and is referred to as

A

Angle Kappa

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3
Q

angle between optical axis & the visual axis at the nodal point

A

Angle Alpha

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4
Q

line passing through the center of the cornea & the lens & meets the retina

A

Optic axis

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5
Q

object of fixation passes thru the nodal point & meets the fovea

A

Visual axis

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6
Q

line joining the fixation point & the center of rotation of the eye

A

Fixation axis

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7
Q

In emmetropic eye, the angle kappa is said to be?

A

Positive. Optic axis usually intersects the retina inside the fovea centralis

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8
Q

In hypermetropic eye, the angle kappa is?

A

More positive, gives the appearance of pseudoexotropia or pseudodivergent squint. (eyeball is shorter)

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9
Q

In myopia the angle kappa is?

A

Absent or negative, leading to pseudoesotropia or convergent squint (eyeball is longer).

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10
Q

Neither of these lines can be seen, and direction of line of vision is judged by the position of angle, hence?

A

The greater the size of a positive angle gamma and kappa the more the eye will appear to look outwards.

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11
Q

The eye appear to look inwards when?

A

The angle gamma is negative.

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12
Q

The emmetropic eye has a positive angle gamma of?

A

Positive angle gamma of 5°

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13
Q

The emmetropic eye has a positive angle gamma of 5° producing an apparent divergence of?

A

Apparent divergence of 10°, regarded as the normal position of the eyes.

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14
Q

Four rectus muscles

A

Superior, Inferior, Lateral, and Medial Rectus

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15
Q

Two obliques

A

Superior and Inferior Oblique

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16
Q

Primary action of rotating the eye in the four cardinal directions; up, down, out, in.

A

Rectus Muscles

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17
Q

arise in fibrous ring around the optic foramen to the nasal side of the axis of eye

A

Rectus Muscle

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18
Q

RM are inserted in the sclera by flat tendinous insertions about?

A

10mm broad

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19
Q

Where is the medial rectus inserted and how many mm?

A

MR is inserted into the sclera and about 5.5mm to the nasal side of corneoscleral margin

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20
Q

Inferior Rectus insertion

A

IR 6.6m below

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21
Q

Lateral Rectus insertion

A

LR 7 mm to the temporal side

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22
Q

Superior Rectus insertion

A

SR 7.75 mm above

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23
Q

Inferior Oblique insertion

A

IR 18mm

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24
Q

Superior Oblique insertion

A

SR 13.8mm - 18.8mm

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25
Q

Primary function is rotation of the globe, and are differently arranged.

A

Oblique Muscles

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26
Q

Superior Oblique arises from common origin at?

A

Apex of the orbit, runs forward to the trochlea (cartilaginous ring at upper & inner angle of orbit) having threaded through this, becomes tendinous.

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27
Q

(SO) The tendon changes its direction completely & runs over the globe under what rectus muscle?

A

Superior Rectus, to attach itself above and lateral to the posterior pole

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28
Q

(SO) The action of the muscle is determined by?

A

Oblique direction of its tendon after it has left the trochlea.

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29
Q

Oblique muscle that maintains a similar direction throughout its course & is the only muscle not arising from the apex of the orbit.

A

Inferior Oblique

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30
Q

Inferior Oblique arises from?

A

IO arises anteriorly from the lower & inner orbital walls near the lacrimal fossa &, running below the Inferior Rectus (IR lies between the glove & IO), finds an insertion in the sclera below & lateral to the posterior pole of the globe.

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31
Q

What are the two types of small muscle cells in EOM

A

Small fibres & Large fibres

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32
Q

A type of small muscle cell in EOM that is located peripherally, have slow twitch response, capable of graded contractions in absence of action potential & have multiple motor end plates (en grappe)

A

Small Fibres

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33
Q

Multiple motor end plates in the small fibres is also known as

A

en grappe

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34
Q

A type of small muscle cell in EOM that is located centrally, have a fast twitch response and have a single motor end plate.

A

Large fibres

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35
Q

The angle gamma is to the nasal side in?

A

Hypermetropia & emmetropia

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36
Q

Primary, Secondary & Tertiary Action of MR & its Innervation

A

Primary: Adduction
Secondary & Tertiary: None
Innervation: CNIII

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37
Q

Primary, Secondary, & Tertiary Action & Innervation of LR

A

Primary: Abduction
Secondary & Tertiary: None
Innervation: CNVI

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38
Q

Primary, Secondary, & Tertiary Action & Innervation of SR

A

Primary: Elevation (best when eye is abducted position)
Secondary: Incyclotorsion
Tertiary: Adduction
Innervation: CNIII

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39
Q

Primary, Secondary, Tertiary Action & Innervation of IR

A

Primary: Depression (best when eye is abducted position)
Secondary: Excyclotorsion
Tertiary: Adduction
Innervation: CNIII

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40
Q

Primary, Secondary, Tertiary action & Innervation of SO

A

Primary: Incycloduction (intortion)
Secondary: Depression
Tertiary: Abduction
Innervation: CNIV

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41
Q

Primary, Secondary, Tertiary action & Innervation of IO

A

Primary: Excycloduction (extortion)
Secondary: Elevation
Tertiary: Abduction
Innervation: CNIII

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41
Q

EOM rotate around a “centre of rotation” which lies in?

A

Horizontal plane some 12 or 13m behind the cornea, in every movement of the globe each muscle is involved by either contraction or inhibition

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41
Q

What are the three types of rotation or “degrees of freedom” possible around the center of rotation?

A
  1. Rotation around the vertical axis (where the globe is turned from side to side) - [Z axis] (MR & LR)
  2. Rotation around the horizontal axis (where the globe is turned upwards & downwards) - [X axis] (SR, IR, IO, SO)
  3. Rotation around the anterioposterior axis (an involuntary movement of torsion; intorsion (upper pole of cornea rotates nasally), extorsion(rotates temporally). [Y axis] (IO, SO, SR, IR)
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41
Q

Every movement of the eye is a “synkinesis”. Not only there is uniocular synkinesis, there is also?

A

In normal circumstances there is always binocular synkinesis

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41
Q

Abduction of one eye is accompanied by adduction of the other- which is also known as?

A

Conjugate movement

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41
Q

The only exception to conjugate movements is?

A

Bilateral adduction of the eyes in convergence and abduction of both eyes in divergence (dysconjugate movements)

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41
Q

Abduction of both eyes in divergence is also known as?

A

Dysconjugate movement

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42
Q

Elevation or depression of one eye is always accompanied by?

A

Elevation or depression of the other.

43
Q

Elevation of both eyes is accompanied by?

A

Slight abduction (divergence), depression by slight adduction (convergence)

44
Q

In these movements the muscles which contract together are called

A

Synergists

45
Q

Muscles which suffer inhibition or muscles that would work in a directly opposite direction are relaxed are called

A

Antagonists

46
Q

Which muscles are involved or synergists & antagonists in Dextroversion?

A

Synergist: RLR & LMR
Antagonist: RMR & LLR

47
Q

Muscles involved (synergist/antagonist) in Laevoversion?

A

Synergist: RMR & LLR
Antagonist: RLR & LMR

48
Q

Synergist & Antagonist in Dextroelevation

A

Synergist: RSR & LIO
Antagonist: RIR & LSO

49
Q

Synergist & Antagonist in Dextrodepression

A

Synergist: RIR & LSO
Antagonist: RSR & LIO

50
Q

Synergist & Antagonist in Laevodepression

A

Synergist: RSO & LIR
Antagonist: RIO & LSR

51
Q

Synergist & Antagonist in Laevoelevation

A

Synergist: RIO & LSR
Antagonist: LIR & RSO

52
Q

both eyes open, attempting to fixate a target, and moving in the same direction

A

Versions

53
Q

both eyes open, fixing a target but moving in opposite directions synchronously, (e.g. convergence or divergence)

A

Vergences

54
Q

only one eye is open, the other covered or closed (monocular movement)

A

Ductions

55
Q

quick fixation movements

A

Saccadic movements

56
Q

slow following movements

A

Pursuit movements

57
Q

During the initiation of eye movement, increased innervation to an extraocular muscle is accompanied by simultaneous inhibition (a reciprocal decrease in innervation) of the direct antagonist of the contracting muscle of the same eye

A

Sherrington’s law of reciprocal innervation

58
Q

During any conjugate eye movement, equal & simultaneous innervation flows to the yoke muscles

A

Hering’s law of equal innervation

59
Q

Supplies all the extrinsic muscles except Lateral Rectus & Superior Oblique, as well as Sphincter Pupillae & Ciliary Muscle.

A

Oculomotor / Third Cranial Nerve (CNIII)

60
Q

Which cranial nerve supplies the Superior Oblique?

A

Trochlear / Fourth Cranial Nerve (CNIV)

61
Q

Which cranial nerve supplies the Lateral Rectus?

A

Abducens / Sixth Cranial Nerve (CNVI)

62
Q

located in the mid-brain, forms a large, continuous mass of nerve cells situated near the midline in the floor of aqueduct of Sylvius beneath the superior colliculus

A

Oculomotor nucleus

63
Q

supplies fibres to the ciliary muscle (accommodation) & sphincter pupillae (constriction of pupil)

A

Edinger-Westphal (& Perlia)

64
Q

a nucleus (central control center) in the brain that manages that lift our upper eyelids

A

Levator Palpebrae

65
Q

this nucleus is further back in midbrain & is unique because its signals cross over to the opposite side before reaching the muscle that moves the eyes

A

Trochlear Nerve

66
Q

this nucleus is even further back in the brainstem & is close to the facial nucleus (related to facial movements)

A

Abducens Nerve

67
Q

A part of Supranuclear center which contains an area responsible for rapid eye movements towards the opposite side for the purpose of fixation

A

Frontal Cortex

67
Q

refers to regions in the Central Nervous System that are located in the cerebral cortex

A

Supranuclear centers

67
Q

A part of Supranuclear center which has an are that controls slow pursuit eye movements to the same side

A

Occipital Cortex

67
Q

initiated in the pyramidal cells of the motor area of the frontal cortex in the second & third frontal convolutions of both sides

A

Voluntary ocular movements

68
Q

depend on vision (fixation, fusional movements, convergence, etc) the psycho-optical reflexes- are centered in the visual cortex of the occipital lobe

A

Involuntary reflex

69
Q

coordinates the position of the eyes when the head is moved in space

A

Statokinetic reflexes

70
Q

coordinates movement of the eyes in respect to movement of the head upon the body

A

Static reflexes

70
Q

if chin is depressed, eyes normally elevate if fixation is maintained, if head is rotated on a vertical axis the eyes maintain fixation as a result of Statokinetic reflexes. These movements are referred to as

A

“Doll’s head”

71
Q

rapid eye movements to direct the fovea to a target whose image is falling peripherally on the retina

A

Saccades

71
Q

During prolonged rotations the optokinetic system sustains compensatory eye speed at the same speed as the head

A

Optokinetic movements

71
Q

following movements to maintain the image of a slowly moving small object on the fovea

A

Smooth pursuit

72
Q

required to maintain foveal position of image an object which may be moving away or towards the observer or may be located near or far away

A

Vergence

72
Q

prevents slipping of the retinal images when the head moves, it moves the eyes at the same speed but in opposite direction as head

A

Vestibulo-ocular reflex

73
Q

maintaining the image of regard on the fovea

A

Fixation

74
Q

an object to one side of the fixation target forms its retinal images upon the temporal side of one retina & upon the nasal side of the other

A

Correspondence

74
Q

same visual direction, objects on the horopter, gives rise to binocular vision, fall within Panum’s fusional area

A

Corresponding points

74
Q

different visual direction, objects in front/behind the horopter, gives rise to binocular diplopia fall outside of Panum’s area

A

Non-corresponding points (disparate points)

75
Q

part of the eye with the sharpest vision

A

Fovea

76
Q

can be demonstrated by rapid-to-and-from movements of the eyes of a person watching passing objects while looking out of the window of a moving train

A

Optokinetic nystagmus (visually induced nystagmus)

77
Q

describes the way the two eyes work together to integrate images seen by each into one image

A

Binocular Vision

77
Q

happens automatically to maintain singe binocular vision

A

Involuntary fusional movements

77
Q

ability to tolerate the prism without developing double vision

A

Reflex fusional capacity

78
Q

occurs when a farther object is bifixated with a near object in view, temporal disparity

A

Heteronymous Physiological Diplopia (Crossed diplopia)

79
Q

when objects are beyond the point of bifixation, nasal disparity

A

Homonymous Diplopia (Uncrossed Diplopia)

80
Q

in context of vision, refers to the inward rotation of both eyes to focus on a near object

A

Convergence

81
Q

Convergence is measured by which unit

A

Metre angle

82
Q

exerted by each eye when eyes are directed to object at distance of 1m of meridian line between two eyes

A

Meter angle convergence

83
Q

closest point at which an object can be seen singly when maximum convergence is exerted

A

Near point of convergence

84
Q

refers to relative position of the eyes when completely at rest, usually at infinity

A

Far point of convergence

84
Q

mechanism by which the eye changes its refractive power by altering the shape of the lens

A

Accommodation

85
Q

What are the normal values for near point & far point of convergence range?

A

Near: 5cm to 10cm
Far: 6 meters or infinity

85
Q

the difference in convergence between far point & near point

A

Amplitude of convergence

86
Q

used to measure objective & subjective convergence & accommodation in 1mm increments

A

RAF Rule

87
Q

Hofstetter formula

A

Min: 15-0.25(age)
Ave: 18.5-0.30(age)
Max: 25-0.40(age)

88
Q

He found out that the AA is from 0.25 to 1D greater when two eyes are used separately

A

Duane

89
Q

when object of regard is placed at a distance of 100cm, this can be seen by an emmetrope clearly by?

A

Placing +1.00D lens in front of the eye or by increasing refractive power of eye by 1.00D

90
Q

pupils become smaller to increase depth of focus & reduce spherical aberration

A

Pupil constriction (Miosis)

91
Q

eyes adjust their focus to see clearly near objects, involves change in shape of the lens controlled by ciliary muscles & zonule fibers

A

Contractions of ciliary muscle

92
Q

eyes move inward to maintain single binocular vision as object becomes closer

A

Convergence

93
Q

When viewing a far object, circularly arranged Muller’s ciliary muscle is relaxed, allowing the lens zonules & suspensory ligaments to pull on the lens, flattening it in the periphery

A

Helmhotz theory

94
Q

Accommodation occurred through increase of zonular tension at the lens equator with contraction of ciliary muscle, & therefore a bulging of the lens in accommodation was created by compression rather than by passive relaxation

A

Tscherning’s theory

95
Q

Pupillary Light pathway

A

Retina-Optic nerve-Optic chiasm-Optic tract-Lateral geniculate body-Pretectal nucleus- Edinger Westphal Nucleus-Ciliary body-Sphincter & papillae

96
Q

If the eyes are abducted 23°, which rectus muscles only elevates & depress not intort, extort or adduct?

A

Superior & Inferior Rectus

97
Q

Which oblique muscle is when adducted 51° will only depress, doesn’t intort or abduct?

A

Superior Oblique

98
Q

angle between the optic axis & the visual axis at the nodal point

A

Angle alpha

99
Q

angle between the visual axis & pupillary plane

A

Angle kappa

100
Q

angle between the optical axis & fixation axis at the center of rotation of the eye

A

Angle gamma

Binocular Vision (2 decks)

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