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Binocular Vision > nystagmus - MEH > Flashcards

nystagmus - MEH Flashcards

1
Q

what is nystagmus?

A

rhythmic oscillation of 1 or both eyes

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2
Q

is nystagmus manifest or latent?

A

can be both

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3
Q

what are the 4 classifications of nystagmus?

A

physiological
pathological
infantile/congenital
acquired

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4
Q

what is physiological nystagmus

A

a form of involuntary eye movement part of the VOR characterised by alternating smooth pursuit in 1 direction and saccadic movements in the other

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5
Q

where does physiological nystagmus occur>

A

extreme lateral gaze

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6
Q

how much of the normal population can give themselves voluntary nystagmus?

A

5%

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7
Q

what is pathological nystagmus?

A

result of damage to 1 or more components of the vestibular system

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8
Q

which parts of the vestibular system can be damaged to cause pathological nystagmus?

A
  • semi-circular canals
  • otilith organs
  • vestibular cerebellum
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9
Q

does pathological nystagmus cause vision impairment?

A

some degree of vision impairment but severity varies widely

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10
Q

what is benign idiopathic congenital nystagmus secondary to?

A
  • visual defect (e.g albinism or retinal dystrophies)
  • neurological deficit (intra-cranial lesion, drug toxicities, stroke, MS)
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11
Q

what are the 2 types of waveforms?

A

jerk and pendular

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12
Q

what is a jerk reflex?

A

a slow drift off the target, followed by a rapid corrective movement

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13
Q

how is the direction of beating of jerk nystagmus defined?

A

the direction of the fast phase of the movement

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14
Q

is the jerk reflex to do with vestibular or optokinetic?

A

vestibular

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15
Q

what is a pendular nystagmus?

A

sinusodial (smooth oscillations)

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16
Q

which direction does pendular nystagmus occur in>

A

can occur in any direction

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17
Q

how do you find out if the nystagmus is jerk or pendular?

A

electronystagmography

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18
Q

what is the amplitude of a waveform?

A

the ‘excursion’ of the nystagmus

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19
Q

what is the frequency of the waveform?

A

number of oscillations per minute

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20
Q

how can you rate the frequency of a waveform?

A

coarse medium or fine

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21
Q

what is the intensity of the waveform?

A

amplitude x frequency

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22
Q

what is a manifest nystagmus?

A

when both eyes are open, may increase when one eye is covered

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23
Q

what is a latent nystagmus

A

only occurs when one eye is covered and steady fixation with both eyes open

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24
Q

what is a latent nystagmus caused by?

A

an early disrupt to BV, e.g unilateral cataract, early onset squint

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25
Q

what age does congenital/early onset nystagmus occur?

A

2 to 6 months

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26
Q

what are the 2 primary forms of congenital nystagmus?

A
  1. sensory deficit nystagmus (SDN)
  2. congenital idiopathic nystagmus (CIN)
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27
Q

how do you differentiate between SDN and CIN?

A

not possible from clinical observation

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28
Q

aetiology of CIN

A

unknown
may be x linked, autosomal dominant or sporadic

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29
Q

aetiology of SDN

A

early macular deprivation e.g. dense bilateral congenital cataracts, retinal cone dysfunction, albinism)

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30
Q

how do you detect SDN

A

careful examination of fundus and media and electro diagnostic testing

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31
Q

what is manifest latent nystagmus associated with?

A

early onset strabismus & DVD

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32
Q

when is a manifest latent nystagmus detected?

A

around 2 years of age, more pronounced if 1 eye is occluded and in abducted position

33
Q

does the waveform change with position of gaze in congenital nystagmus?

A

yes it can do (e.g. pendular in pp, jerk in lateral gaze)

34
Q

what is the direction of nystagmus in congenital nystagmus?

A

horizotal (uniplanar - horizontal in all directions of gaze including up gaze and down gaze)

35
Q

what is the null zone?

A

position of gaze of least head movement and VA is best

36
Q

what might a px do for the best VA?

A

px may adopt abnormal head posture for best VA

37
Q

what vision testing do you do in someone with nystagmus>

A
  1. with AND without AHP (monocular and both eyes)
38
Q

what is the VA in CIN?

A

can be 6/9

39
Q

what is the VA in SDN?

A

often 6/60 or less

40
Q

what is an indicator for active management?

A

significant AHP

41
Q

how do you test px’s near vision in nystagmus?

A
  • test at px’s preferred distance
  • write down AHP and distance
42
Q

what increases nystagmus?

A

may increase on occlusion. Nystagmus is normally similar in both eyes

43
Q

what is seen in some px’s with congenital nystagmus?

A

head nodding (HN)

44
Q

what is spasmus nutans?

A

rare condition presenting at 1 or 2 months with nystagmus, HN, AHP

45
Q

when does spasmus nutans resolve?

A

by 3 years

46
Q

what is spasmus nutans caused by?

A

tumours ON, optic chiasm, 3rd ventricle

47
Q

what is oscillopsia?

A

an illusion of an unstable vision, made up of the perception of to-and-fro movement of the environment

48
Q

what is a strong sign of acquired nystagmus?

A

oscillopsia

49
Q

what is voluntary nystagmus also known as?

A

psychogenic

50
Q

what is voluntary nystagmus?

A

brief high frequency horizontal nystagmus that cannot be sustained for more than ~5 seconds

51
Q

how does voluntary nystagmus present?

A

as acquired nystagmus with oscillopsia and possible head nodding

52
Q

what is the management of nystagmus>?

A

no cure but many helpful treatments (only cure for underlying conditions)

53
Q

why is onward referral to an ophthalmologist important?

A

diagnosis of initial condition
potentially consult a geneticist

54
Q

how do you manage congenital nystagmus?

A
  • refraction and correction of all refractive error
  • accurate assessment of near (1/3m and preferred distance) and distance VA
  • ophthalmologist may arrange paediatric assessment and genetic counselling
  • assessment of consistence and significance of any AHP
  • monitoring through children
55
Q

what are some treatment options for congenital? (6)

A
  • glasses/CLs
  • low vision aids
  • prisms
  • drugs
  • botox
  • surgery
56
Q

what would be better for correcting nystagmus - glasses or cls? AND WHY

A

contact lenses - they move with the eye therefore ensure best corrected vision in all planes

57
Q

how do low vision aids help?

A
  • magnifiers can help with reading
  • tinted glasses can help with glare
  • can help children struggling with school work
58
Q

why are prisms not the best option for nystagmus?

A

limited success rate esp if null zone in extreme periphery

59
Q

what prisms could you give to force convergence?

A

base IN prisms on both eyes

60
Q

if the null zone is on the left, and therefore AHP is on the right , which prisms do you give?

A

BO RE and BI LE

61
Q

how do you incorporate prism ?

A

first as a fresnel then applied to glasses if happy

62
Q

what are the 2 most commonly used drugs in treatment?

A

gabapentin and memantine - BUT DOES NOT WORK FOR EVERYONE

63
Q

how many listed drugs are there for the treatment of acquired nystagmus?

A

17 - inlcuding alcohol and cannabis

64
Q

how does botox help with acquired nystagmus?

A

reduce symptoms of oscillopsia BUT effects are temporary

65
Q

what is the treatment for reducing AHP?

A

prisms to move visual environment to null point
prisms to reduce nystagmus through forced convergence
surgery to EOMs to move null zone to primary position

66
Q

why must you wait until child is 8 to suggest surgery to EOMs for AHP?

A

surgery is of little value if AHP is less than 15 degrees,, so wait until 8 to fully evaluate AHP and px is visually mature

67
Q

what are the results of surgery for nystagmus?

A

-Usually improves but may not abolish AHP
- Effect may not last may need “re-do” Sx
- May improve vision
- Most patients will not reach driving standard

68
Q

what is biofeedback?

A

treatment technique combining auditory, visual and tactile feedback and visual attention
gives voluntary control over nystagmus but no practical long term advantage in vision

69
Q

which type of nystagmus represents intracranial pathology?

A

acquired nystagmus ( MS, CVA, tumours, head trauma)

70
Q

how do you differentially diagnose between congenital and acquired?

A

HISTORY- onset, signs & symptoms

71
Q

cause of abducting nystagmus?

A

lesion to medial longitudinal folliculus MLF

72
Q

what are the 4 different treatment options for acquired nystagmus?

A
  • drugs
  • surgery to shift null zone
  • retrobulbar botox (limited success)
  • removal of cause may help
73
Q

which of these options is not an example of physiological nystagmus?
1. optokinetic
2. vestibular
3. retinal dystrophies
4. voluntary

A

retinal dystrophies

74
Q

Which of the following is the correct definition for nystagmus:
1. Rhythmic oscillation of one or both eyes
2. Asymmetrical oscillation of one or both eyes
3. Horizontal jerky movements with reduced vision
4. Circular motion of one or both eyes

A
  1. Rhythmic oscillation of one or both eyes
75
Q

A 34 year old presents with acquired nystagmus and complaining of oscillopsia, which of the following would you not offer this patient?
1. Prisms if there is a null zone
2. Surgery to reduce AHP
3. Drugs to reduce nystagmus
4. Contact lens trial.

A
  1. Surgery to reduce AHP
76
Q

Which of the following statements are incorrect with regards to waveforms?
1. Often only revealed by electronystagmography
2. May be a combination of jerk/pendular
3. May vary with gaze direction
4. Symmetrical in both eyes with electronystagmograph

A
  1. Symmetrical in both eyes with electronystagmograph
77
Q
A
78
Q
A

Binocular Vision (30 decks)

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