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Opthalmo > Strabismus > Flashcards

Strabismus Flashcards

1
Q

What is binocular single vision?

A

Two images from two eyes combine to form one central image

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2
Q

What is Stereopsis?

A

3D depth perception

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3
Q

Which is greater? Binocular acuity or monocular acuity?

A

Binocular acuity

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4
Q

What is the importance of Stereopsis and Binocular single vision?

A

1) Increase field of vision
2) Eliminate the blind spot
3) Depth perception
4) Estimation of distance

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5
Q

Binocular eye movements are called __.

A

Versions

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6
Q

Monocular eye movements with the other eye covered are called __.

A

Ductions

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7
Q

What are the 6 muscles of the eye?

A

1) Medial Rectus
2) Lateral Rectus
3) Superior Rectus
4) Inferior Rectus
5) Superior Oblique
6) Inferior Oblique

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8
Q

Which muscles of the eye does the third cranial nerve (Oculomotor) supply?

A

1) Medial Rectus
2) Superior Rectus
3) Inferior Rectus
4) Inferior Oblique

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9
Q

Which muscle of the eye does the fourth cranial nerve (Trochlear) supply?

A

Superior Oblique

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10
Q

Which muscle of the eye does the fifth cranial nerve (Trigeminal) supply?

A

Lateral Rectus

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11
Q

The total number of the positions of gaze is _.

A

9

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12
Q

What are Yoke muscles?

A

A pair of muscles (one muscle in each eye) moving the eye to the same direction of gaze

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13
Q

What is squint (strabismus)?

A

Misaligned eyes (both eyes are not looking in the same direction)

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14
Q

What is concomitant (non-paralytic) squint?

A

The angle of deviation is not affected by the direction of gaze. (Eye muscles all move normally)

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15
Q

What causes concomitant (non-paralytic) squint?

A

UNCLEAR IMAGES AS A RESULT OF:
1) Refractive error
2) Opacities in the media of eye
3) Abnormalities of the retina that prevent the translation of a correctly formed image into neural impulses

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16
Q

Is concomitant (non-paralytic) squint congenital or acquired?

A

Congenital

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17
Q

Is non-concomitant (paralytic) squint congenital or acquired?

A

Acquired

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18
Q

When is diplopia at its peak in non-concomitant (paralytic) squint?

A

When attempting to look in
the direction requiring the action of the weak muscle.

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19
Q

What is non-concomitant (paralytic) squint?

A

The degree of misalignment varies with direction of the gaze (An eye muscle is not functioning properly)

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20
Q

Non-concomitant (paralytic) squint may indicate:

A

1) A nerve palsy
2) An extra-ocular muscle disease

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21
Q

Which nerve palsies may cause non-concomitant (paralytic) squint?

A

1) 6th nerve (Abducens)
2) 4th nerve (Trochlear)
3) 3rd nerve (Oculomotor)

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22
Q

What does a 6th nerve palsy cause?

A

Failure of Abduction

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23
Q

What does a 4th nerve palsy cause?

A

Defective depression of the eye when in adduction

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24
Q

What does a 3rd nerve palsy cause?

A

1) Failure of adduction, elevation and depression of the eye
2) Ptosis
3) Dilated pupil

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25
Q

What causes dysthyroid eye disease?

A

Infiltration of the extraocular muscles with lymphocytes and the depositions of glycosaminoglycans

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26
Q

Which muscle is most commonly affect in dysthyroid eye disease?

A

Inferior rectus

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27
Q

What are the complications of dysthyroid eye disease?

A

1) Chemosis & corneal ulcers = corneal perforations
2) Compressive optic neuropathy = blindness

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28
Q

Management of dysthyroid eye disease?

A

1) Systemic steroids
2) Radiotherapy
3) Surgical orbital decompression
4) Prisms

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29
Q

How do you diagnose myasthenia gravis?

A

Edrophonium test

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30
Q

How do you treat myasthenia gravis?

A

1) Neostigmine (acetylcholine esterase inhibitor)
2) Thymectomy

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31
Q

What is ocular myositis?

A

Inflammation of the extraocular muscles

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32
Q

Signs and symptoms of ocular myositis?

A

1) Pain
2) Diplopia
3) Restriction of movement

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33
Q

Mode of inheritance of Ocular Myopathy?

A

Mitochondrial DNA mutation

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34
Q

Describe the eye movement in ocular myopathy?

A

Slowly and symmetrically
reduced

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35
Q

What is seen pathologically in ocular myopathy?

A

Ragged red fibers

36
Q

What is Brown’s syndrome also called?

A

Superior oblique tendon sheath syndrome

37
Q

What is Brown’s syndrome?

A

Movement of inferior oblique muscle is restricted by the superior oblique muscle tendon failing to pass smoothly through its trochlear pulley or a stiff inelastic tendon

38
Q

Brown’s syndrome results in:

A

Restriction of elevation in adduction

39
Q

Duane’s Syndrome is caused by:

A

Faulty innervation of the medial and lateral rectus muscles

40
Q

Duane’s Syndrome results in:

A

Faulty abduction and adduction

41
Q

Do children in Duane’s syndrome develop amblyopia?

A

No, because binocular alignment is normal is some gaze positions

42
Q

What is the Parapontine Reticular Formation
(PPRF)?

A

A part of the pontine reticular formation involved in the coordination of horizontal eye movements

43
Q

What happens if there is a lesion in the Parapontine Reticular Formation
(PPRF)?

A

Horizontal gaze palsy to the side of the lesion

44
Q

When do we normally see lesions in the Parapontine Reticular Formation
(PPRF)?

A

1) Brainstem disease
2) Vascular diseases
3) Tumors

45
Q

What is Internuclear ophthalmoplegia?

A

Conjugate lateral gaze in which the affected eye shows impairment of adduction

46
Q

If the right eye is affected in Internuclear ophthalmoplegia, what will the patient see?

A

They will see double when looking to the left

47
Q

What does divergence of the eyes lead to in Internuclear ophthalmoplegia?

A

Horizontal diplopia

48
Q

What does convergence of the eyes lead to in Internuclear ophthalmoplegia?

A

Nothing. It is preserved

49
Q

What causes Internuclear ophthalmoplegia?

A

Injury to MLF (medial longitudinal fasciculus)

50
Q

What is the cover test?

A

A test to detect strabismus

51
Q

Cover test: If the unaffected eye is covered and the affected eye moves outward, it is:

A

Esotropic

52
Q

Cover test: If the unaffected eye is covered and the eye moves inward, it is:

A

Exotropic

53
Q

Cover test: If the unaffected eye is covered and the eye moves upward, it is:

A

Hypotropic

54
Q

Cover test: If the unaffected eye is covered and the eye moves downward, it is:

A

Hypertropic

55
Q

What is the Hirschberg corneal light reflex?

A

Objective assessment of ocular alignment

56
Q

What are the signs of pseudoesotropia?

A

1) Small Interpupillary distance
2) Epicanthal folds
3) Flat nasal bridge

57
Q

What are the signs of Infantile Esotropia?

A

1) Not associated with hypermetropia
2) Large angle of deviation
3) Both eyes are convergent (crossed fixation)
4) Left fovea fixes right field & vice versa

58
Q

How do you assess infantile esotropia?

A

1) Fixation reflex
2) Cover uncover test
3) Refraction by cycloplegic drugs
4) Fundoscopy to evaluate any organic disease (retinoblastoma)

59
Q

How do you treat infantile esotropia?

A

Surgery (recession of both medial recti)

60
Q

What is Mobius Syndrome?

A

6th and 7th nerve underdevelopment

61
Q

Signs & symptoms of Mobius Syndrome?

A

1) Crossed eyes (bilateral 6th)
2) Lack of facial expression
(facial palsy)
3) Clubbed feet
4) Missing fingers or toes
5) Chest wall anomalies

62
Q

The combination of these three movements (__, __ and __) is under the control of the Edinger-Westphal nucleus and is referred to as the near triad.

A

1) Accommodation
2) Convergence
3) Miosis

63
Q

The combination of these three movements (accommodation, convergence and miosis) is under the control of the ____ and is referred to as the near triad.

A

Edinger-Westphal nucleus

64
Q

The combination of these three movements (accommodation, convergence and miosis) is under the control of the Edinger-Westphal nucleus and is referred to as the ___.

A

Near triad

65
Q

Accommodative esotropia occurs as a consequence of:

A

A reduction in zonular tension induced by ciliary muscle contraction

66
Q

Accommodative esotropia is often seen in patients with
a moderate amount of:

A

Hypermetropia

67
Q

What are the 2 types of Accommodative Esotropia?

A

1) Fully accommodative esotropia
2) Convergence excess esotropia

68
Q

Non-accommodative esotropia is induced by:

A

1) Emotional or physical stress (illness)
2) Sensory deprivation (untreated congenital cataract,
optic atrophy)
3) Retinoblastoma

69
Q

What are the causes of intermittent exodeviations?

A

1) Divergence excess
2) Convergence weakness
3) Basic

70
Q

What are the causes of constant exodeviations?

A

1) Congenital
2) Sensory
3) Consecutive

71
Q

Intermittent exodeviations manifest during times of:

A

1) Visual inattention
2) Fatigue
3) Stress
4) During illness

72
Q

If intermittent exodeviation is exposed to bright light, it
causes:

A

Reflex closure of one eye

73
Q

What are the types of concomitant exotropia?

A

1) Accommodative exotropia
2) Non-accommodative exotropia
3) Consecutive exotropia

74
Q

Accommodative exotropia is associated with:

A

Uncorrected myopia

75
Q

Treatment for accommodative exotropia?

A

Correct myopia

76
Q

Accommodative exotropia can be seen when the child looks:

A

Far away

77
Q

What is Crouzon’s syndrome (branchial arch syndrome)/Non-accommodative exotropia caused by?

A

Defect in Fibroblast growth factor receptor 2 (Autosomal Dominant, Chromosome 10)

78
Q

Signs & symptoms of Crouzon’s syndrome (branchial arch syndrome)/Non accommodative exotropia?

A

1) Shallow eye sockets after early fusion of surrounding bones

2) Cranial synostosis

3) Hypertelorism (greater than normal distance between the
eyes)

4) Patent ductus arteriosus

5) Aortic coarctation

79
Q

Secondary exotropia is seen in cases of:

A

Unilateral loss of vision

80
Q

Consecutive exotropia is due to:

A

Surgical overcorrection of an esodeviation

81
Q

What causes amblyopia?

A

1) Suppression (monocular or cortical process producing absolute scotoma)
2) Non-use of the retino-cortical pathway

82
Q

What are the types of amblyopia?

A

1) Strabismic
2) Anisometropic
3) Form Deprivation

83
Q

Adult-onset strabismus usually causes __ rather than amblyopia, since the two eyes are not fixated on the same object.

A

Double vision

84
Q

Refractive amblyopia may result from:

A

Anisometropia (unequal refractive error between the two eyes)

85
Q

Amblyopia is associated with a
combination of __ and __.

A

Anisometropia; Strabismus

85
Q
A

Opthalmo (10 decks)

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