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Strabismus & Ocular Motility > Alphabet Patterns > Flashcards

Alphabet Patterns Flashcards

1
Q

What is a physiological V pattern defined as?

A

A physiological tendency for divergence on elevation. To be physiological we’d be looking at a <15 difference from depression to elevation

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2
Q

What is a pathological V pattern defined as?

A

> 15PD difference from depression to elevation

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3
Q

What is a pathological A pattern defined as?

A

> 10PD from elevation to depression

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4
Q

What are the alphabet patterns?

A

V, A, X, Y, Inverted Y & Diamond

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5
Q

What is this pattern?
5BO Elevation
15BO pp
30BO Depression

A

V Eso

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6
Q

What is this pattern?
30BO Elevation
15BO pp
5BO Depression

A

A Eso

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7
Q

What is this pattern?
5BI Elevation
15BI pp
30BI Depression

A

A Exo

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8
Q

What is this pattern?
30BI Elevation
15BI pp
5BI Depression

A

V Exo

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9
Q

What is this pattern?
35BI Elevation
25BI pp
10BI Depression

A

V Exo

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10
Q

What is this pattern?
10BO Elevation
25BO pp
35BO Depression

A

V Eso

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11
Q

What is this pattern?
10BI Elevation
25BI pp
35BI Depression

A

A Exo

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12
Q

What is this pattern?
35BO Elevation
25BO pp
10BO Depression

A

A Eso

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13
Q

What is the prevalence of A or V patterns in horizontal strabismus?

A

12 - 50%

V 2x as common as A

A Exo more common than A Eso

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14
Q

What is Antimongoloid?

A

Downward slanting palpebral fissures

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15
Q

What pattern is someone with Antimongoloid likely to have?

A

More likely to have a V pattern

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16
Q

What is Mongoloid?

A

Upward slating palpebral fissures

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17
Q

What pattern is someone with Mongoloid likely to have?

A

More likely to have an A pattern

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18
Q

What orbital anomalies often display A and V-patterns?

A

Craniosynostosis (abnormally shaped skulls due to premature fusion of sagittal and frontal sutures at birth), such as Crouzon, Apert and Pfeiffer syndromes and plagiocephaly, often display A- and V-patterns owing to orbital anomalies

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19
Q

What pattern is associated with an ET with IO o/a?

A

V Pattern

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20
Q

What pattern is associated with an XT with IO o/a?

A

V Pattern

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21
Q

What pattern is associated with an XT with SO o/a?

A

A pattern

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22
Q

What pattern is associated with an ET with SO o/a?

A

A pattern
(as more divergence looking down)

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23
Q

What vertically acting muscle weakness is a V Eso associated with?

A

SO weakness

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24
Q

What vertically acting muscle weakness is a V Eso associated with? What happens in depression and in elevation?

A

SO weakness

In depression: –> less abduction + o/a of IR = increased adduction

In elevation: o/a of IO gives relatively more abduction + u/a of SR = less adduction

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25
Q

What vertically acting muscle weakness is a V Exo associated with?

A

SR weakness

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26
Q

What vertically acting muscle weakness is a V Exo associated with? What happens in depression and in elevation?

A

SR weakness

In elevation: –> less adduction + o/a of IO = increases abduction

In depression: o/a of IR gives relatively more adduction & u/a of SO = less abduction

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27
Q

What vertically acting muscle weakness is an A Eso associated with?

A

IO weakness

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28
Q

What vertically acting muscle weakness is a A Eso associated with? What happens in depression and in elevation?

A

IO weakness

In elevation: –>less abduction + o/a of SR = increases adduction

In depression: o/a of SO gives relatively more abduction + u/a of IR = less adduction

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29
Q

What vertically acting muscle weakness is a A Exo associated with?

A

IR weakness

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30
Q

What vertically acting muscle weakness is a A Exo associated with? What happens in depression and in elevation?

A

IR weakness

In depression: –>less adduction + o/a of SO = increases abduction

In elevation: o/a of SR cause relatively more adduction & u/a of IO = less abduction

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31
Q

Are A or V patterns most common in unilateral or bilateral weakness?

A

Bilateral weakness

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32
Q

In a V eso what horizontal muscle is o/a or u/a?

A

o/a of MR

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33
Q

In an A eso what horizontal muscle is o/a or u/a?

A

u/a of MR

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34
Q

In a V exo what horizontal muscle is o/a or u/a?

A

o/a of LR

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35
Q

In a V eso what horizontal muscle is o/a or u/a?

A

u/a of LR

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36
Q

Why is it that exo’s are associated with LR and eso’s with MR?

A

Theory is based on the hypothesis:

  • Lateral recti work more for distance and on elevation
  • Medial recti work more for near and on depression
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37
Q

In a V Exo where is the LR insertion?

A

Too low

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38
Q

In a V Exo if the LR is too low what does this mean?

A

It causes more slack of LR muscle on depression (i.e. less divergence) and on elevation LR are at an increased mechanical advantage, causing increased divergence.

This weakens the primary action of the muscle in downgaze and increases it in upgaze.

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39
Q

In a V Eso if the MR is too high what does this mean?

A

It causes more slack of MR on elevation (i.e. less convergence) and on depression the MR are at an increased mechanical advantage, causing increased convergence.

If a medial rectus muscle is infraplaced, a new force vector for depression will be created.

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40
Q

In an A Eso if the LR is too high what does this mean?

A

It causes more tension of the LR on depression (i.e. more abduction/divergence) and on elevation causes more slack of the LR (i.e. less abduction/divergence) =

More convergence in elevation and less convergence in depression

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41
Q

In an A Exo if the MR is too low what does this mean?

A

It causes more tension of the MR in elevation (i.e. more convergence) but causes the MR to be more slack in depression (i.e. less convergence)

More convergence in elevation and less convergence in depression

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42
Q

What does an oblique muscle insertion being too anterior mean?

A

It weakens it

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43
Q

What does an oblique muscle insertion being too posterior mean?

A

It strengthens it

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44
Q

What oblique muscle insertion could a V Eso have?

A

SO too anterior

45
Q

What does it mean if a V Eso has a SO that’s too anterior?

A

The abducting force of the SO is weakened and as this works mainly in depression there is relatively more convergence in depression, therefore giving a V Eso pattern

46
Q

What oblique muscle insertion could a V Exo have?

A

IO too posterior

47
Q

What does it mean if a V Exo has a SO that’s too posterior?

A

The abducting force of the IO is strengthened and as this works mainly in elevation there is relatively more divergence in elevation, therefore giving a V Exo pattern

48
Q

What oblique muscle insertion could an A Eso have?

A

IO too anterior

49
Q

What does it mean if an A Eso has a IO that’s too anterior?

A

The abducting force of the IO is weakened and this works mainly in elevation so there is relatively more convergence in in elevation therefore giving an A pattern Eso

50
Q

What oblique muscle insertion could an A Exo have?

A

A SO that’s too posterior

51
Q

What does it mean if an A Exo has a SO that’s too posterior?

A

The abducting force of the SO is strengthened, and as this mainly works in depression, there is relatively more divergence in depression, therefore giving an A Exo pattern

52
Q

How might vertical recti muscles be abnormally positioned in a V eso?

A

IR insertion too nasal (medial) –> increase in adduction by IR on depression

53
Q

How might vertical recti muscles be abnormally positioned in a V exo?

A

SR insertion too temporal –> less adduction by SR on elevation

54
Q

How might vertical recti muscles be abnormally positioned in a A eso?

A

SR insertion too nasal –> increase in adduction by SR on elevation

55
Q

How might vertical recti muscles be abnormally positioned in a A exo?

A

IR insertion too temporal –> less adduction by IR on depression

56
Q

In eso deviations are the vertical recti muscle insertions too medial or too temporal?

A

Too medial

57
Q

In exo deviations are the vertical recti muscle insertions too medial or too temporal?

A

Too temporal

58
Q

How might Sagittalisation affect vertical actions of muscles and cause an A or V pattern?

A

A dysfunction of the oblique muscles caused by differences b/w the planes of SO and IO

The normal axes of the SO and Io muscles are approx parallel. If one insertion is more posterior than normal the muscles axis lies in a more sagittal plane i.e. It is closer to the anterior posterior axis of globe.

The need to compensate for the cyclo-deviation caused will alter the degree of contraction by the vertical muscles and therefore, also influence their vertical actions. Thus causing an A or V pattern.

59
Q

What does sagittalisation of the IO mean?

A

The angle between the IO and visual axis is reduced compared to the angle between visual axis and SO due to the origin being too anterior or the insertion too posterior

60
Q

What does sagittalisation of the IO cause?

A

It reduces the IO’s torsional action thus causing incyclotropia.

As the IO and IR contract to try to compensate for this which results in excessive adduction on depression and excessive abduction on elevation often then showing as an o/a IO with a V pattern

61
Q

What sagittalisation can cause a V-pattern?

A

Sagittalisation of IO cause o/a of IO and increased abduction on upgaze

62
Q

What sagittalisation can cause an A-pattern?

A

Sagittalisation of SO causes o/a of SO and increase in abduction on downgaze

63
Q

What are muscle pulleys?

A

Connective tissue pulleys have been identified as functional mechanical origins of the EOM. Normally stable during gaze shifts.

64
Q

What happens when muscle pulleys are not where we except them to be in terms of the MR and LR?

A

A-exo (MR lower than LR)

V-exo (MR higher than LR)

Clark et al. (1998)

65
Q

What is the association of torsion to alphabet patterns?

A

Association of excyclotorsion with V pattern and incyclotorsion with A pattern

66
Q

What torsion does a V pattern cause? Where might the LR pulley be?

A

V-pattern characterised by excyclorotation of the orbits; LR pulley is located too low relative to the medial rectus pulley (Demer, 2014)

67
Q

What can loss of fusion lead to in terms of torsion and alphabet patterns?

A

Guyton (1988, 1992), Deng et al (2013) loss of fusion predisposes the oculomotor system to cyclodeviations of the eyes which in turn causes A and V patterns

68
Q

What might mongoloid lead to in terms of alphabet patterns and muscle actions?

A

A pattern and SO over-action

69
Q

What might antimongoloid lead to in terms of alphabet patterns and muscle actions?

A

V pattern and IO over-action

70
Q

How is Down’s Syndrome related to alphabet pattern and muscle actions?

A

Downs syndrome is often associated with A pattern esotropia and SO o/a

71
Q

What elevators are affected in V patterns?

A

Elevators: o/a of IO and u/a of SR =
Greater relative divergence

72
Q

What depressors are affected in V patterns?

A

u/a of SO and o/a of IR =
Greater relative convergence

73
Q

What elevators are affected in A patterns?

A

Elevators: u/a of IO and o/a of SR =
Greater relative convergence

74
Q

What depressors are affected in A patterns?

A

Depressors: o/a of SO and u/a of IR =
Greater relative divergence

75
Q

What tests can you use to diagnose an alphabet pattern?

A
  • CT & OMs
  • Measurements in PP, direct elevation and depression
  • PCT
    6m to eliminate accommodation. May also want to measure at 1/3m if interested in what happens when accommodate.
  • Synoptophore
  • Lees screen
  • Field of BSV
76
Q

Why would we want to manage an alphabet pattern?

A
  • To create a larger and more useful field of BSV
  • To achieve a better ocular alignment
  • To reduce the risk of consecutive exotropia and give a more stable angle
77
Q

What do we need to gain from the investigation into alphabet patterns?

A
  • Symptomatic
    Diplopia, Constant, Intermittent e.g. Decompensate on prolonged reading,
    Asthenopic
  • Ocular alignment
  • Objective assessment of torsion
    Indirect ophthalmoscopy or fundus photography
  • Potential for BSV or retaining BSV
  • Assess risk of over-correcting a patient requiring strabismus surgery
  • Assess value of combining strabismus surgery & correcting alphabet pattern at the same time
78
Q

What surgery do we need to do in alphabet patterns?

A

Surgery may depend on aetiology or the presence of significant oblique over-actio

79
Q

What are some surgical principles when it comes to whether to operate on vertical or horizontal muscles?

A

If associated vertical muscle over- & under-actions: operate on vertical muscles

If no/ mild vertical muscle over- & under-actions: operate on horizontal muscles

80
Q

What is the aim of surgery in V pattern with IO over-action?

A

Weakening of the IO muscle allows more convergence on elevation i.e. cause SR over-action increased ad-duction due to the o/a they have of the IO

81
Q

What are the surgical options for V pattern IO overaction?

A
  • IO recession
  • IO myectomy
  • Anterior transposition of IO

Horizontal surgery (recess/resect) performed at same time or subsequent sitting

Anterior transposition of IO as advocated by Gobin now mostly used in DVD

In acquired bilateral SO palsy with V-Eso
- Harado-Ito or SO tuck will reduce V pattern

82
Q

What surgery to we do in acquired bilateral SO palsy with V-Eso?

A

Harado-Ito or SO tuck will reduce V pattern

83
Q

What is the aim of A pattern with SO overaction?

A

Weakening the SO muscle allows more convergence on depression i.e. cause IR over-action = increased adduction

84
Q

What are the surgical options of an A pattern with SO overaction?

A
  • SO posterior tenectomy
  • SO posterior tenotomy
  • SO z-tenotomy
  • SO split lengthening
  • SO tendon spacer (silicon expander; makes tendon longer)
  • Operate on both SO if moderate/marked o/a of SO
  • Alternative
    Bilateral IR resection

Horizontal surgery (recess/resect) performed at same time or subsequent sitting

Combining SO Z-tenotomy, SO posterior tenectomy or tenotomy, and recess/resect of horizontal rectus muscles

85
Q

What is the aim of A pattern with SR overaction?

A

Weakening of both SR muscles allows more divergence on elevation i.e. cause IO over-action increased ab-duction

86
Q

What are the surgical options of A pattern with SR overaction?

A

Bilateral SR recession but could also do a bilateral IO recession

87
Q

When might we transpose horizontal muscles?

A

We can do a bilateral recession and transposition of muscles by moving the LR in exo deviations and the MR in eso deviations

We move it in the direction of the greatest deviation so:
- Insertion of MR moved towards apex (less convergence this way)
- Insertion of LR moved towards wide end

When moving the insertion down it cause the action of that muscle to be more slack on depression

88
Q

When transposing the MR where do we move it towards?

A

Towards apex to cause less convergence

89
Q

When transposing the LR where do we move it towards?

A

Towards the wide end

90
Q

When we move the insertion down what does it cause of the muscle?

A

When moving the insertion down it cause the action of that muscle to be more slack on depression

91
Q

What muscle do we transpose, and where, in V Eso’s?

A

Transpose MR insertion downwards

92
Q

What muscle do we transpose, and where, in A Eso’s?

A

Transpose MR insertion upwards

93
Q

What muscle do we transpose, and where, in V Exo’s?

A

Transpose LR insertion upwards

94
Q

What muscle do we transpose, and where, in A Exo’s?

A

Transpose LR insertion downwards

95
Q

When might be transpose horizontal muscles instead of other surgical options?

A

Advocated if no or minimal oblique muscle over- and under-actions

Also possible to combine recess/resect procedure, moving one up & one down

Complications: risk of torsional disturbances if work on one eye

96
Q

What are the risks of transposing horizontal muscles?

A

Complications: risk of torsional disturbances if work on one eye

97
Q

What is it called when we combine horizontal surgery with the slanting of muscle insertions?

A

Boyd’s technique

98
Q

When might we use the surgical technique of slanting horizontal muscle insertions?

A

Advocated in the absence of marked over-actions of the oblique muscles

99
Q

What complications are there from slanting of muscle insertions?

A
  • Correcting A-exo can result in SO weakening
  • Vertical displacement of horizontal muscles may induce torsion
100
Q

How does horizontal muscle insertion work as a surgical technique?

A

Horizontal muscle tension is stronger at upper margin than at lower margin on elevation.

101
Q

What horizontal slanting surgery do we do to reduce V exo?

A

Upper margin of LR recessed > than lower margin to reduce V-exotropia
i.e. less ab-duction on elevation: close V

102
Q

What horizontal slanting surgery do we do to reduce A exo?

A

Lower margin of LR recessed > than upper margin to reduce A-exotropia
i.e. less ab-duction on depression: close A

103
Q

What horizontal slanting surgery do we do to reduce A eso?

A

Upper margin of MR recessed > than lower margin to reduce A-esotropia
i.e. less ad-duction on elevation: opens A

104
Q

What horizontal slanting surgery do we do to reduce V eso?

A

Lower margin of MR recessed > than upper margin to reduce V-esotropia
i.e. less ad-duction on depression: opens V

105
Q

When might a surgery be modified to prevent an A exo post-op?

A
  • When performing horizontal muscle surgery
  • Consecutive XT may be associated with A-patterns due to SO overaction
  • Large recession of IR for Graves Orbitopathy moves insertions nasally which will prevent A exo post-op
106
Q

How might we modify a horizontal muscle surgery to prevent an A exo post-op?

A
  • Abnormally low insertion of MR is noted. This muscle may be transposed upwards.
  • If the insertion of the LR muscle is found to be abnormally high this muscle may be transposed downwards.
  • This will minimise the risk of an A-exo post-operatively
107
Q

How might we modify a surgery in a consecutive XT that’s associated with A pattern due to SO o/a to prevent an A exo post-op?

A

Combined horizontal muscle surgery with SO weakening procedure may reduce the risk of A exo post-operatively

108
Q

How might we modify a surgery in a large recession of IR for Graves Orbitopathy to prevent an A exo post-op?

A

Moving insertions nasally will prevent an A exo post-op
i.e. moving insertion nasally increases ad-duction, moving insertion temporally decreases ad-duction

Strabismus & Ocular Motility (23 decks)

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