nystagmus - MEH

Question 1

what is nystagmus?

Answer 1

rhythmic oscillation of 1 or both eyes

Question 2

is nystagmus manifest or latent?

Answer 2

can be both

Question 3

what are the 4 classifications of nystagmus?

Answer 3

physiological
pathological
infantile/congenital
acquired

Question 4

what is physiological nystagmus

Answer 4

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

Question 5

where does physiological nystagmus occur>

Answer 5

extreme lateral gaze

Question 6

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

Answer 6

5%

Question 7

what is pathological nystagmus?

Answer 7

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

Question 8

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

Answer 8

• semi-circular canals
• otilith organs
• vestibular cerebellum

Question 9

does pathological nystagmus cause vision impairment?

Answer 9

some degree of vision impairment but severity varies widely

Question 10

what is benign idiopathic congenital nystagmus secondary to?

Answer 10

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

Question 11

what are the 2 types of waveforms?

Answer 11

jerk and pendular

Question 12

what is a jerk reflex?

Answer 12

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

Question 13

how is the direction of beating of jerk nystagmus defined?

Answer 13

the direction of the fast phase of the movement

Question 14

is the jerk reflex to do with vestibular or optokinetic?

Answer 14

vestibular

Question 15

what is a pendular nystagmus?

Answer 15

sinusodial (smooth oscillations)

Question 16

which direction does pendular nystagmus occur in>

Answer 16

can occur in any direction

Question 17

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

Answer 17

electronystagmography

Question 18

what is the amplitude of a waveform?

Answer 18

the ‘excursion’ of the nystagmus

Question 19

what is the frequency of the waveform?

Answer 19

number of oscillations per minute

Question 20

how can you rate the frequency of a waveform?

Answer 20

coarse medium or fine

Question 21

what is the intensity of the waveform?

Answer 21

amplitude x frequency

Question 22

what is a manifest nystagmus?

Answer 22

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

Question 23

what is a latent nystagmus

Answer 23

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

Question 24

what is a latent nystagmus caused by?

Answer 24

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

Question 25

what age does congenital/early onset nystagmus occur?

Answer 25

2 to 6 months

Question 26

what are the 2 primary forms of congenital nystagmus?

Answer 26

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

Question 27

how do you differentiate between SDN and CIN?

Answer 27

not possible from clinical observation

Question 28

aetiology of CIN

Answer 28

unknown may be x linked, autosomal dominant or sporadic

Question 29

aetiology of SDN

Answer 29

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

Question 30

how do you detect SDN

Answer 30

careful examination of fundus and media and electro diagnostic testing

Question 31

what is manifest latent nystagmus associated with?

Answer 31

early onset strabismus & DVD

Question 32

when is a manifest latent nystagmus detected?

Answer 32

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

Question 33

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

Answer 33

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

Question 34

what is the direction of nystagmus in congenital nystagmus?

Answer 34

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

Question 35

what is the null zone?

Answer 35

position of gaze of least head movement and VA is best

Question 36

what might a px do for the best VA?

Answer 36

px may adopt abnormal head posture for best VA

Question 37

what vision testing do you do in someone with nystagmus>

Answer 37

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

Question 38

what is the VA in CIN?

Answer 38

can be 6/9

Question 39

what is the VA in SDN?

Answer 39

often 6/60 or less

Question 40

what is an indicator for active management?

Answer 40

significant AHP

Question 41

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

Answer 41

- test at px's preferred distance - write down AHP and distance

Question 42

what increases nystagmus?

Answer 42

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

Question 43

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

Answer 43

head nodding (HN)

Question 44

what is spasmus nutans?

Answer 44

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

Question 45

when does spasmus nutans resolve?

Answer 45

by 3 years

Question 46

what is spasmus nutans caused by?

Answer 46

tumours ON, optic chiasm, 3rd ventricle

Question 47

what is oscillopsia?

Answer 47

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

Question 48

what is a strong sign of acquired nystagmus?

Answer 48

oscillopsia

Question 49

what is voluntary nystagmus also known as?

Answer 49

psychogenic

Question 50

what is voluntary nystagmus?

Answer 50

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

Question 51

how does voluntary nystagmus present?

Answer 51

as acquired nystagmus with oscillopsia and possible head nodding

Question 52

what is the management of nystagmus>?

Answer 52

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

Question 53

why is onward referral to an ophthalmologist important?

Answer 53

diagnosis of initial condition potentially consult a geneticist

Question 54

how do you manage congenital nystagmus?

Answer 54

- 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

Question 55

what are some treatment options for congenital? (6)

Answer 55

- glasses/CLs - low vision aids - prisms - drugs - botox - surgery

Question 56

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

Answer 56

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

Question 57

how do low vision aids help?

Answer 57

- magnifiers can help with reading - tinted glasses can help with glare - can help children struggling with school work

Question 58

why are prisms not the best option for nystagmus?

Answer 58

limited success rate esp if null zone in extreme periphery

Question 59

what prisms could you give to force convergence?

Answer 59

base IN prisms on both eyes

Question 60

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

Answer 60

BO RE and BI LE

Question 61

how do you incorporate prism ?

Answer 61

first as a fresnel then applied to glasses if happy

Question 62

what are the 2 most commonly used drugs in treatment?

Answer 62

gabapentin and memantine - BUT DOES NOT WORK FOR EVERYONE

Question 63

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

Answer 63

17 - inlcuding alcohol and cannabis

Question 64

how does botox help with acquired nystagmus?

Answer 64

reduce symptoms of oscillopsia BUT effects are temporary

Question 65

what is the treatment for reducing AHP?

Answer 65

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

Question 66

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

Answer 66

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

Question 67

what are the results of surgery for nystagmus?

Answer 67

-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

Question 68

what is biofeedback?

Answer 68

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

Question 69

which type of nystagmus represents intracranial pathology?

Answer 69

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

Question 70

how do you differentially diagnose between congenital and acquired?

Answer 70

HISTORY- onset, signs & symptoms

Question 71

cause of abducting nystagmus?

Answer 71

lesion to medial longitudinal folliculus MLF

Question 72

what are the 4 different treatment options for acquired nystagmus?

Answer 72

- drugs - surgery to shift null zone - retrobulbar botox (limited success) - removal of cause may help

Question 73

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

Answer 73

retinal dystrophies

Question 74

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

Answer 74

1. Rhythmic oscillation of one or both eyes

Question 75

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.

Answer 75

2. Surgery to reduce AHP

Question 76

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

Answer 76

4. Symmetrical in both eyes with electronystagmograph