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A - MSRA Ophthalmology [14] > [12] Strabismus > Flashcards

[12] Strabismus Flashcards

1
Q

What is strabismus also known as?

A

Squint

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2
Q

What is strabismus?

A

Misalignment of the eyes

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3
Q

What happens as a result of the misalignment of the eyes in strabismus?

A

The retinal image is not in the corresponding area of both eyes which may cause diplopia in adults or amblyopia in children

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4
Q

What is amblyopia?

A

Lazy eye

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5
Q

How is strabismus most commonly described?

A

By the direction of the eye misalignment

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6
Q

What is the suffix for manifest squints?

A

-tropia

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7
Q

What prefix is used for an inward ocular deviation in strabismus?

A

eso-

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8
Q

What prefix is used for an outward ocular deviation in strabismus?

A

exo-

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9
Q

When can the severity of a horizontal squint (eso/exo) vary?

A

With up/down gaze

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10
Q

If deviation is greater in an upward gaze what pattern does the squint follow?

A

V pattern

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11
Q

If the deviation is greater in a downward gaze, what pattern does the squint follow ?

A

A pattern

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12
Q

What prefix is used for an upward ocular deviation in strabismus?

A

hyper-

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13
Q

What prefix is used for a downward ocular deviation in strabismus?

A

hypo-

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14
Q

Are vertical or horizontal squints more common?

A

Horizontal

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15
Q

What is a manifest squint?

A

A squint present when the eyes are open and being used

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16
Q

What is another term for a manifest squint?

A

Heterotropia

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17
Q

What is it called when eyes are perfectly aligned?

A

Orthophoria

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18
Q

What is a latent squint?

A

When the eye deviates when it is covered or closed

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19
Q

What suffix is used for a latent squint?

A

-phoria

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20
Q

Do most people have orthophoria?

A

No, most people have a mild latent squint

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21
Q

What is the mild latent squint that most people have called?

A

Heterophoria

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22
Q

What are the different ways of classifying a squint?

A
  • Congenital or Acquired
  • Right, Left or Alternating
  • Permanent or Intermittent
  • Manifest or Latent
  • Concomitant or Incomitant
  • Primary, Secondary or Consecutive
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23
Q

When is a squint congenital?

A

If onset is before 6 months of age

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24
Q

What is an alternating squint?

A

The patient can alternate fixation between right and left eye - usually spontaneous but can be voluntary

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25
Q

What is another term for a concomitant squint?

A

Non-paralytic

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26
Q

What is another term for an incomitant squint?

A

Paralytic

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27
Q

What happens in a concomitant squint?

A

The size of the deviation does not vary with direction of gaze

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28
Q

When do concomitant squints normally begin?

A

Typically between 2-4 years

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29
Q

What type of squint is mostly concomitant?

A

Esotropias

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30
Q

What happens in an incomitant squint?

A

The direction of gaze affects the size or presence of the squint

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31
Q

When can incomitant squints arise?

A

Childhood or adulthood

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32
Q

What causes incomitant squints?

A

Problems with the muscles controlling eye movement

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33
Q

What sort of problems with they extra-ocular muscles can lead to incomitant squint?

A
  • Neurological problems
  • Mechanical problems
  • Myogenic problems
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34
Q

Are most squints primary, secondary or consecutive?

A

Primary

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35
Q

What is a secondary squint?

A

Arises due to loss or impairment of vision

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36
Q

What is a consecutive squint?

A

Arises following overcorrection

37
Q

How do most concomitant squints arise?

A

Congenital

38
Q

How are children with concomitant squints eye movements affected?

A

Should be unaffected when tested separately

39
Q

Do children with concomitant squints have problems with their extra-ocular muscles or cranial nerves?

A

No

40
Q

Do children with concomitant squints have diplopia?

A

No

41
Q

What happens to the longitudinal axes of the eyes in people with concomitant squints when eye movements are tested?

A

Remain the same

42
Q

What usually causes a paralytic squint?

A

Damage to the extra-ocular muscles or their nerves

43
Q

What is a common symptom in paralytic squint?

A

Diplopia

44
Q

When is diplopia often at its worst in paralytic squint?

A

In the direction of gaze produced by the weak muscle

45
Q

What nerves can be involved in producing a paralytic squint?

A
  • CN III
  • CN IV
  • CN VI
46
Q

How many nerves can be affected in paralytic squint?

A

One or more

47
Q

What disorders of childhood can squint be more common in?

A
  • CP
  • Down’s syndrome
  • Hydrocephalus
  • SOL
48
Q

What is the leading cause of strabismus in adults?

A

Stroke

49
Q

What are some less common causes of strabismus in adults?

A
  • Neurological problems
  • Grave’s disease
  • Trauma
  • Infection
50
Q

What can the cause of paralytic squint often vary depending upon?

A

The nerve that is affected

51
Q

What are some causes of paralytic squint caused by CN III damage?

A
  • Ischaemic microvascular disease
  • Aneurysm
  • Tumour
  • Herpes zoster
52
Q

What are some causes of paralytic squint caused by CN IV damage?

A
  • Trauma
  • Vasculopathy
  • Demyelinating disease
53
Q

What can vasculopathy causing squint often be associated with?

A
  • Diabetes

- Hypertension

54
Q

What are some causes of paralytic squint caused by CN VI damage?

A
  • Vasculopathy
  • Trauma
  • Idiopathic
55
Q

What are the risk factors for squint?

A
  • Family history
  • Prematurity
  • Refractive error
56
Q

How do most non-paralytic squints present in children?

A

With parental concern due to manifest squint

57
Q

How else can non-paralytic squints present in children?

A
  • Intermittent closing of one eye especially in sunlight
  • Reduced motor skills
  • Pre-school screening
  • Compensatory head tilt or chin lift
58
Q

Why may children with non-paralytic squint have a compensatory head tilt or shin lift?

A

To minimise diplopia

59
Q

What is the most common symptom of non-paralytic squint in adults?

A

Diplopia

60
Q

What are some other symptoms of non-paralytic squint in adults?

A
  • Asthenopia
  • Eye strain
  • Headaches
  • Pulling sensation
  • Noticing misaligned eyes
61
Q

What is asthenopia?

A

Ocular discomfort

62
Q

What does the presentation of a paralytic squint largely depends on?

A

The nerve that is affected

63
Q

What are some features of a squint caused by CN III palsy?

A
  • External ophthalmoplegia (partial or complete)
  • Internal ophthalmoplegia
  • Ptosis
64
Q

What are some features of a squint caused by CN IV palsy?

A
  • Binocular vertical diplopia
  • Difficulty in reading
  • Sense things appear to be tilted
65
Q

What are some features of a squint caused by CN VI palsy?

A
  • Horizontal diplopia worse for distance vision and on lateral gaze of affected side
66
Q

What does the presentation of a multiple nerve plays causing squint depend on?

A

The combination of nerves involved

67
Q

What is common feature of squint caused by multiple nerve palsies?

A

Limitation of a range of eye movements and diplopia

68
Q

What are some additional features of squint caused by multiple nerve palsies?

A
  • Facial pain
  • Ptosis
  • Small pupil
69
Q

What screening methods are used in assessing squint?

A
  • Gross inspection
  • Light reflex tests
  • Cover tests
  • Visual acuity
  • Ophthalmoscopy
70
Q

How is a cover test conducted?

A
  • Object held in front of patient
  • Patient focuses on object
  • Occlude one eye for several seconds and observe other eye for movement
  • As the covered eye is uncovered, observe it for movement
71
Q

What does the cover test show if the covered eye moves outwards as it is uncovered?

A

Esotropia in the covered eye (was initially turned inwards)

72
Q

What does the cover test show if the covered eye moves inwards as it is uncovered?

A

Exotropia in the covered eye (was initially turned outward)

73
Q

What additional test can be tried if the cover test is normal?

A

Alternative cover test

74
Q

What happens in the alternative cover test?

A

Occluder is rapidly moved from one eye to the other and observe for movement

75
Q

What are the differentials for squint?

A
  • Pseudostrabismus
  • Blurred vision
  • Monocular diplopia
  • Convergence insufficiency
76
Q

What is the treatment of a non-paralytic squint guided by?

A

The nature for the squint and age of the patient

77
Q

What is the first step in the management of non-paralytic squints?

A

Management of refractive errors

78
Q

What will need treating in patients <8 with non-paralytic squint?

A

Concurrent amblyopia

79
Q

How is amblyopia treated?

A

Eye patching +/- cycloplegic drops

80
Q

What can patients have to correct non-paralytic squint if it is big enough or resists conservative management?

A

Surgical alignment

81
Q

How can surgical alignment of squints be performed?

A

A combination of muscle resection and antagonistic resection to restore binocular function

82
Q

Where should patients with paralytic squints be referred?

A

Ophthalmology for investigation

83
Q

What further investigations may be performed for paralytic squint?

A
  • Orthoptic assessment
  • Blood tests
  • Imaging
84
Q

What can patients be given whilst the underlying cause of a paralytic squint is managed?

A

Prisms (fixed onto glasses) to alleviate diplopia

85
Q

What can uncorrected squint lead to?

A

Amblyopia lazy eye

86
Q

What can be a complication of corrective surgery for squint?

A

Under- or over-correction requiring further surgery

87
Q

What are some other complications of squint?

A

Psychosocial consequences

88
Q

Why can squint cause psychosocial consequences?

A

Because people may find it disturbing to look at or worry that is the case

A - MSRA Ophthalmology [14] (16 decks)

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