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Binocular Vision > Incomitancy - MEH > Flashcards

Incomitancy - MEH Flashcards

1
Q

What is the definition of incomitancy?

A

The angle of deviation varies in size (can be larger or smaller) in different positions of gaze + the angle of deviation is greatest in the direction of limitation of eye movement

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2
Q

What are two ways to classify incomitancy?

A

Acquired and congenital

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3
Q

What is essential with acquired incomitancies?

A

Referral is essential as it requires further investigation

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4
Q

What are four ways incomitant strabismus is classified?

A
  • Neurogenic
  • Myogenic
  • Mechanical
  • Dysinnervational
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5
Q

How is a neurogenic incomitant strabismus caused?

A

A lesion with the nerve supplying the muscle

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6
Q

How is a myogenic incomitant strabismus caused

A

A lesion directly affecting the muscle itself

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7
Q

How is a mechanical incomitant strabismus caused?

A

A lesion within the orbit that interferes with muscle action

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8
Q

How is a dysinnervational incomitant strabismus caused

A

Resulting in developmental error in innervation of the muscle

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9
Q

Which two incomitant strabismus’ are similar ?

A

Neurogenic and myogenic
Mechanical and dysinnervational

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10
Q

What are three examples of a neurogenic strabismus?

A

III, IV and VI cranial nerve palsies
Double elevator palsy
Double depressor palsy

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11
Q

What are characteristics of a left 4th nerve palsy?

A

Left hypertropia which increases as px looks to the right and decreases when px looks to the left

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12
Q

What are examples of myogenic strabismus?

A

Myaesthenia Gravis and chronic progressive external ophthalmoplegia (CPEO)

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13
Q

What are three examples of mechanical strabismus?

A
  1. Browns Syndrome
  2. thyroid eye disease
  3. orbital fracture
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14
Q

What are two examples of dysinnervational disorders?

A

Duanes retraction syndrome, and congenital fibrosis of EOM

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15
Q

What is sheringtons law?

A

Unilocular law which involves the agonist muscle contracting with equal and simultaneous relaxation of the direct antagonist

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16
Q

What is Hering’s law?

A

Binocular law of which equal and simultaneous contraction of contralateral synergist muscle (the opposite eye)

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17
Q

Can you name where the muscles are acting in each gaze?

A

No? You are gonna fail if you do not know this simple stuff

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18
Q

What are the four steps of a muscle sequelae ?

A

1) Primary muscle u/a
2) O/a of contralateral synergist (the other eye)
3) O/a of ipsilateral direct antagonist (same eye)
4) U/a of antagonist of contralateral synergist

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19
Q

Does a full muscle sequelae develop over time or over a acute onset in neurogenic and myogenic incomitant strabismus?

A

Over time

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20
Q

Why is hard to differentiate the primary under actor from congenital palsies?

A

Due to a fully developed sequelae difficult to differentiate which is the primary under actor and underacting antagonist contralateral synergist

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21
Q

What are four things we must address which doing an orthoptic assessment for a incomitant strabismus?

A

1) Make a differential diagnosis
2) Asses stability or monitor change of ophthalmoplegia
3) Presence and strength of BSV
4) Management both temporary and long term

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22
Q

What tests would you do for someone with an incomitant strabismus and what would each of them indicate ?

A
  • Observations (facial asymmetry & CHP)
  • Ocular motility (pain on eye movement + globe retraction)
  • PCT in 9 positions of gaze
  • Synoptophore (torsion would be seen)
  • BSV ( particular attention to fusional amplitude)
  • Hess chart
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23
Q

What three signs would someone with a COMPENSATED incomitant strabismus show?

A
  • Asymptomatic of diplopia
  • Adopts CHP
  • Increased fusional amplitude
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24
Q

What three signs would someone with a DECOMPENSATED incomitant strabismus show?

A
  • Manifest deviation
  • Diplopia with aesthenopic sx
  • Suppression but this is more likely to occur with longstanding/children
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25
Q

Is a CHP in just acquired, just congenital or both?

A

Both

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26
Q

What are six reasons for why a CHP is used?

A
  • Achieve SV
  • Centralise field of BSV
  • Avoid area where there is dipl/pain/discomfort
  • Increased separation if diplopic images
  • Ptosis
  • Nystagmus
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27
Q

What are three components of a CHP?

A
  • Face turn
  • Head tilt (overcome height or torsion)
  • Chin elevation of depression
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28
Q

What CHP would someone with a horizontal deviation have?

A

Adopt a face turn

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29
Q

What CHP would someone with a vertical deviation have?

A

FT in direction of vertical action
Head tilt towards lower eye
Chin in direction of worst affected gaze position

30
Q

Should a CT be assessed or without a head posture?

A

Both

31
Q

Should OM be tested with or without a head posture?

A

Without

32
Q

What are five characteristics of a neurogenic incomitancy? (Like deviations and stuff)

A
  • Deviation in pp reflects extent extent of palsy
  • Duction > versions
  • Saccadic movement may be slow in paretic eye
  • No globe retraction
  • AHP tilt in vertical palsies
33
Q

What are five characteristics of a mechanical incomitancy? (Like deviations and stuff)

A
  • Small deviation in pp
  • Duction = versions
  • Saccadic movement the velocity is normal until point of limitation occurs
  • May have globe retraction, pain or discomfort
  • AHP tilt rare
34
Q

What are the three purposes of a Hess chart?

A
  • Allows ocular movements to be represented graphically
  • Demonstrates muscle sequelae
  • Assists in differential diagnosis
35
Q

What a three conditioNS in Hess charts?

A
  • Px must have foveal fixation
  • NRC
  • Sufficient vision in either eye to locate fixation points
36
Q

How many degrees are represented in each square of a Hess chart?

A

5

37
Q

Which eye does a smaller field belong to?

A

Affected eye

38
Q

How is an under action represented in a Hess chart?

A

Inward displacement

39
Q

How is a mechanical restriction represented on a Hess chart?

A

Narrow field restricted in opposing directions

40
Q

What does an equal sized field on a Hess chart denote?

A

Symmetrical limitation in BE/ non paralytic strab/ spread of concomitance

41
Q

What chart can be used to plot separation of images?

A

Diplopia chart

42
Q

What does a field of BSV demonstrate and how is it measured and represented?

A

Area of BSV, measured using the arc perimeter and the area of bsv is marked with hatching

43
Q

Do you know how to differential diagnose between congential and acquired?

A
44
Q

Do you know how to differentially diagnose between neurogenic and mechanical?

A
45
Q

Not a flash card but go through the px scenarios in the incomitancy lecture slides.

A

Not a flash card but go through the px scenarios in the incomitancy lecture slides.

46
Q

Will a px with congenital incomitancy experience diplopia?

A

No or may be intermittent

47
Q

Will a px with an acquired incomitancy experience diplopia?

A

Yes and will be able to tell u exact onset

48
Q

Will a px with a congenital incomitancy be aware of a CHP?

A

No but they have one

49
Q

Will a px with a aquired incomitancy be aware of a CHP?

A

Yes and find is uncomfortable to maintain

50
Q

Will a px with a congenital incomitancy have a full muscle sequelae?

A

Yes, difficult to find under actor on Hess

51
Q

Will a px with a aquired incomitancy have a full muscle sequelae?

A

No, normally just step 1 & 2 (easy to see on Hess)

52
Q

Will a px with a congenital incomitancy have a normal fusional amplitude range?

A

No they would have extended ranges for vertical deviations (like a SO palsy)

53
Q

Will a px with an acquired incomitancy have a normal fusional amplitude range?

A

Yes

54
Q

Will a px with a congenital incomitancy suppress?

A

Yes with intermittent diplopia

55
Q

Will a px with an aquired incomitancy suppress?

A

No unless very poor vision

56
Q

In congenital SO palsy, would torsion be noted?

A

No

57
Q

In acquried SO palsy, would torsion be noted?

A

Yes

58
Q

Would there be a PP deviation in neurogenic incomitancies?

A

Yes, Marked

59
Q

Would there be a PP deviation in mechanical incomitancies?

A

Yes, but small

60
Q

Does diplopia remain the same or reverse in neurogenic incomitancies?

A

Remains the same

61
Q

Does diplopia remain the same or reverse in mechanical incomitancies?

A

Can reverse

62
Q

With neurogenic incomitancies, what is the relationship between duction and versions?

A

Movement is greater on duction then versions

63
Q

With mechanical incomitancies, what is the relationship between duction and versions?

A

Ductions and versions same

64
Q

With a neurogenic incomitancy, is a Hess chart compressed or equally spaced?

A

Equally spaced, but slightly smaller for the affected eyes

65
Q

With a mechanical incomitancy, is a Hess chart compressed or equally spaced?

A

Compressed

66
Q

With a neurogenic incomitancy, will a px experience pain?

A

Uncommon

67
Q

With a mechanical incomitancy, will a px experience pain?

A

Yes, it is Common

68
Q

Will IOP change and if so by how much with a neurogenic incomitancy?

A

Remains Unchanged

69
Q

Will IOP change and if so by how much with a mechanical incomitancy?

A

Rises by 5mmHg when looking AWAY from limitation

70
Q

Is this mechanical or neurogenic?

A

Mechanical

71
Q

Is this mechanical or neurogenic?

A

Neurogenic but not fully developed

72
Q
A

Binocular Vision (30 decks)

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