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Binocular vision, visual impairment and paediatrics > Nystagmus > Flashcards

Nystagmus Flashcards

1
Q

What is nystagmus:

A

Rhythmic, repetitive and involuntary movement of eyes up down, side to side or circular motion

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2
Q

Features of nystagmus:

A
  • Movements can be horizontal, vertical, torsional or a combination
  • Manifest or latent
  • 1 in 1,000 cases of the general population
  • Both eyes can move together or independently of each other
  • A person with nystagmus has no control over movement of their eye
  • Is most common form of visual impairment in children
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3
Q

Classification of nystagmus:

A
  • Physiological
  • Pathological
  • Infantile / Congenital
  • Acquired
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4
Q

What are the 4 types of physiological nystagmus:

A
  1. Opto-kinetic (OKN)
    ○ Response to a moving scene (train)
    ○ A nystagmus induced by looking at moving visual stimuli.
  2. Vestibular (VOR)
    ○ Response to rotation of the head (light and dark)
    ○ Alternating smooth pursuits in one direction and saccadic movements in the other direction
  3. End point
    ○ In extreme lateral gaze
  4. Voluntary
    ○ 5% of the normal population
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5
Q

Example of pathological nystagmus:

A

Benign congenital idiopathic nystagmus

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6
Q

What is pathological nystagmus the result of:

A

Damage to one or more components of the vestibular system E.G. semicircular canals, otolith organs, and the vestibular cerebellum.

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7
Q

What does pathological nystagmus cause:

A

Visual impairment

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8
Q

What can congenital idiopathic nystagmus be secondary to:

A
  • Visual deficit (Sensory deficit nystagmus) SDN
    • E.g. albinism
    • E.G. Retinal dystrophies
      OR
  • Neurological deficit
    • E..G Intra-cranial lesions
    • E.G. Drug toxicities
    • E.G. Stroke
      E.G. Multiple sclerosis
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9
Q

How are optokinetic i.e pendular and vertibular i.e jerk nystagmus revealed:

A
  • By electronystagmography
  • Only revealed by carrying out eye movement recordings.
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10
Q

What is jerk nystagmus:

A
  • A slow phase (pathological) and fast phase (refixation) i.e a slow drift off the target, followed by a rapid corrective movement
  • Described by direction of saccade e.g. right beat; upbeat; downbeat
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11
Q

What is pendular nystagmus:

A
  • No fast phase - sinusoidal
  • Can occur in any direction, torsional, horizontal, vertical, or even a combination of these.
  • Smooth oscillations
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12
Q

What are the commonest types of nystagmus waveforms:

A
  • Pendula
  • Pendula with foveating saccades
  • Pseudo-cylcoid
  • Jerk with extended foveation
  • Jerk nystagmus
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13
Q

What is the direction of beating of the nystagmus defined by:

A

The direction of the fast phase of the movement.

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14
Q

What are the features of waveforms in nystagmus:

A
  • May be a combination of jerk/pendular nystagmus
  • May vary with gaze direction
  • Can be complex!
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15
Q

What is amplitude:

A

The ‘excursion’ of the nystagmus

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16
Q

What is frequency:

A

Number of oscillations per minute - ‘coarse, medium or fine’

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17
Q

What is intensity:

A

Amplitude x frequency

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18
Q

What is manifest nystagmus:

A

Present when both eyes are open but may increase when one eye is covered

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19
Q

What is latent nystagmus:

A
  • Present when one eye is covered, usually have steady fixation with both eyes open
  • This may be the result of an early insult to binocular vision e.g. unilateral cataract, early onset squint
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20
Q

When is congenital nystagmus usually present from:

A

Around two to six months of age.

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21
Q

What are the two primary forms of congenital nystagmus:

A
  1. Sensory deficits nystagmus
  2. Congenital idiopathic nystagmus.
    - It is not possible to differentiate between these two forms purely from a clinical observation of their nystagmus.
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22
Q

Aetiology/cause of congenital idiopathic nystagmus:

A
  • The cause is most likely unknown.
  • There is some suggestions that it could be X-linked, autosomal dominant or even sporadic.
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23
Q

Aetiology/cause of sensory deficits nystagmus:

A
  • Due to early macular deprivation
  • E.G. patients who have dense bilateral cataracts, retinal cone dysfunction, albinism, which is ocular cutaneous or purely ocular.
  • Careful examination of the fundus and media as well as electrode diagnostic testing is required for these patients.
  • Sensory deficit nystagmus is very under diagnosed.
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24
Q

How is manifest latent nystagmus different from manifest latent nystagmus:

A

Separate diagnosis

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25
Q

What is manifest latent nystagmus associated with:

A

Early Onset Strabismus & DVD

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26
Q

When is manifest latent nystagmus detected:

A

Around 2 years of age

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27
Q

When is manifest latent nystagmus worsened:

A

If 1 eye is occluded and in abducted position of gaze

28
Q

Describe the waveform in congenital nystagmus:

A
  • Waveform may change during infancy
    • May initially present as large roving eye movements, developing into pendular/jerk
    • Waveform may vary with position of gaze
      ○ E.G. when the patient looks in primary position, this will look more like a pendular nystagmus. However, in lateral gaze, this may look more like jerk nystagmus.
29
Q

Direction of congenital nystagmus:

A
  • Almost invariably horizontal in waveform (may have rotary component)
  • Uniplanar nystagmus indicates this horizontal nystagmus is the same in all directions of gaze, this includes elevation and looking down into depression.
30
Q

What does null zone mean in nystagmus:

A

The direction of gaze in which the eyes of someone with nystagmus are most stable. And therefore the vision is at its best

31
Q

Features of null zone:

A
  • In this position of gaze is the least movement of the eyes (damping of the nystagmus )
  • To achieve this area of null zone, the patient may adopt an abnormal head posture to move their head into a position where the nystagmus is least and vision is best
  • Management implications and one reason for referral to ophthalmologist
32
Q

Assessing VA in patients who have any form of nystagmus:

A
  • With and without their abnormal head posture (monocularly and binocularly )
  • VA better in CIN (can be 6/9) SDN - often 6/60 or less
  • Significant AHP indicator for active management (refer)
33
Q

VA in congenital idiopathic nystagmus vs sensory deficits nystagmus:

A
  • VA of congenital idiopathic nystagmus can be as good as 6/9
  • But those with sensory deficits nystagmus usually have poorer VA of approximately 6/60 or even less
34
Q

What does it mean if px with nystagmus has a significant abnormal head posture:

A

This is an indicator for some active management and this patient would need to be referred onward to a hospital eye service for consideration of further treatment.

35
Q

Testing near vision in px’s with nystagmus:

A

Test at patient’s preferred distance

36
Q

What would we need to record for when testing near vision in px’s with nystagmus:

A
  • The abnormal head posture
  • The testing distance that they prefer to hold the book at.
  • E.G. if they read N5 and this was held 8cm away from them, = N5 @ 8cms
37
Q

What can px’s with congenital idiopathic nystagmus achieve for near vision testing:

A

N5

38
Q

Other features of congenital nystagmus:

A
  • Nystagmus usually similar in both eyes
  • May increase on occlusion of one eye
  • May be associated with strabismus
39
Q

What is present in some px’s with congenital nystagmus:

A

Head nodding - but usually disappear over time

40
Q

What can head bobbing and torticollis be:

A

Compensatory mechanisms that improve vision by reducing the frequency and asymmetry of the nystagmus

41
Q

What is spasm nutans:

A
  • A disorder affecting infants and young children.
  • It involves rapid, uncontrolled eye movements, head bopping, and sometimes holding the neck in an abnormal position.
  • This is a rare condition presenting within the first two years of life.
  • This condition is self limiting and usually the disorder disappears by the age of approximately three or four years of age.
  • There are rare cases that Spasmus nutans is associated with chiasmal or suprachiasmal small lesions in the brain, thus warranting neuroimaging on baby’s diagnosed with this disorder.
42
Q

When do px’s complain of oscillopsia:

A

Oscillopsia is not usually a presenting sign in congenital nystagmus
But may be present when:
* They are tired
* When their nystagmus increases
* In the dark

43
Q

What is complaints of oscillopsia suggestive of:

A

Acquired or voluntary nystagmus

44
Q

What is voluntary nystagmus:

A
  • Usually a brief, high-frequency horizontal nystagmus that cannot be sustained for more than about five seconds.
  • An acquired form of nystagmus whereby patients are troubled by oscillopsia and possible head nodding.
  • The nystagmus is rapid and consists of poorly sustained back-to-back saccades, which are usually horizontal in direction.
  • Voluntary nystagmus is best confirmed by eye movement recordings.
45
Q

Management of nystagmus:

A
  • There is currently no cure for nystagmus
  • But some underlying conditions can be treated, especially childhood cataracts and strabismus.
  • And there are therapies for some neurological conditions.
  • Make sure any site difficulties are corrected by prescription glasses or contact lenses, such as short-sightedness, long sightedness, or even astigmatism
46
Q

What is the management of congenital nystagmus:

A
  • Refraction and correction of all refractive errors
  • Accurate assessment of near and distance VA
  • Near VA recorded at 1/3m and their preferred distance.
  • All children presenting with nystagmus would need a cycloplegic refraction, and all correction of refractive errors should be corrected
  • Ophthalmologist may arrange a paediatric assessment and possible genetic counselling.
  • The presence and significance of any abnormal head posture needs to be monitored on a visit basis.
  • Monitoring through childhood
47
Q

Treatment options for nystagmus px’s:

A
  • Glasses / Contact lenses
  • Low vision aids
  • Prisms
  • Drugs
  • Botulinum Toxin
  • Surgical corrections of eye movements
48
Q

Refractive correction treatment for nystagmus px’s:

A
  • Glasses if find any underlying refractive error – to ensure best possible corrected vision
  • Contact lenses – move with the eye therefore ensures best corrected vision.
49
Q

Low vision aids treatment for nystagmus px’s:

A
  • Low vision aids will be helpful for those school-age children who are struggling with their schoolwork.
  • There are various different types of magnifiers available which can help with reading.
  • Tinted glasses will also help with any glare.
  • Will require LVA assessment in first instance
50
Q

How successful are prisms in px’s with nystagmus:

A

Prisms have a limited success rates in patients with nystagmus, especially if their null zone is in the extreme positions of gaze.

51
Q

Treatment of prisms for px’s with nystagmus:

A

Temporary Fresnel prisms can be given in the first instance, which are applied to their glasses and can be incorporated into their glasses

52
Q

How do prisms help px’s with nystagmus - example:

A
  • If the patient has a null zone to the left, they will adopt a phase turn i.e head position to their right
  • Thus moving the images to the left i.e towards their null zone.
  • So they will require Base out prism to the right eye and base in prism to the left eye.
  • This will ensure px’s eyes fixate in the left gaze, but without the need to use an abnormal head posture.
  • If the patient shows significant reduction of the nystagmus in convergence then base in prisms in both eyes will force them to converge their eyes.
  • This is usually limited to those patients who do have binocular single vision and adequate motor fusion.
  • The strength of the prisms would need to be the same strength in both lens. Just the direction of this prism will be different in size.
53
Q

Drugs used for management of treatments of acquired nystagmus:

A
  • 17 listed drugs for the treatment of acquired nystagmus
  • List includes alcohol and cannabis
  • Gabapentin, baclofen and Memantine most commonly used
  • Different drugs may be better for different types of nystagmus
54
Q

Botulinum Toxin injections:

A
  • Can be helpful with acquired nystagmus associated with multiple sclerosis
  • Though these are not usually effective in people with Congenital nystagmus
  • Effects are temporary but can reduce symptoms of oscillopsia
55
Q

Treatment to reduce abnormal head posture:

A
  • Surgery to EOMs to move null zone to primary position
    • Little value if the abnormal head posture is less than 15 degrees
    • Usually wait until the child is around eight years of age so they are visually mature and it’s possible to evaluate the effect of the abnormal head posture
  • Prisms can also be used to move the visual environment with the use of fresnel prisms so the null point can be moved and seen in a primary position
  • Prisms to reduce nystagmus through forced convergence with the use of base in prisms.
56
Q

When is surgery option:

A

Some centers offer eye surgery to children and adults with nystagmus where there is a marked head-turn due to a null point.

57
Q

Surgery for px’s with nystagmus where there is a marked head-turn due to a null point:

A
  • The procedure involves detachment and reattachment of the eye muscles.
  • The result is usually a more natural head position so that the patient can look straight ahead to focus on faces and objects and sometimes they report that the vision is clearer.
  • Follow-up surgery is sometimes needed to refine any correction.
  • Some people perceive a slowing of the eye movements as a result of surgery.
  • Though, this is thought to be anecdotal and could simply be due to the change in the position of the null point.
  • Face turn to right, null zone to left
  • Sx moves BEs in direction of AHP to centre the null zone
  • Surgery will not correct nystagmus but helpful in reducing need for abnormal head posture to their null Zone
58
Q

How effective is nystagmus surgery:

A

Nystagmus surgery aims to reduce the amplitude of nystagmus with either improvements of visual acuity or a reduction of bothersome head posture.

59
Q

What is the most common reason for patients seeking surgical treatment for nystagmus:

A

To allow them to acquire a driving license.

60
Q

What is the principle underlying surgical treatment for nystagmus:

A
  • To rotate the eyes in the direction of the head-turn.
  • So to produce a relative gaze palsy towards the site to which the eyes are normally directed.
61
Q

Other treatment for congenital nystagmus:

A
  • Contact lenses may be preferable to spectacles in high ametropia or eccentric null zone for both sensory and motor wise
    • They provide proprioceptive information regarding changes in eye position that can be used by the patient to control and reduce the nystagmus
  • Biofeedback training
    • May give some voluntary control over nystagmus but no practical long term advantage in vision
    • A technique combining auditory, visual, and tactile feedback, along with visual attention, visual imagery and relaxation techniques to train oculomotor control
62
Q

How is acquired nystagmus different from congenital nystagmus:

A
  • Different clinical characteristics from congenital nystagmus
  • Usually represents intracranial pathology (e.g. multiple sclerosis, CVA, tumours, head trauma)
  • Presents with known onset and oscillopsia
63
Q

Differential diagnosis - congenital/acquired:

A
  • History - onset, signs & symptoms
  • Associated neurological signs
  • Any associated or recent neurological illnesses.
  • Clinical characteristics of nystagmus
  • Are they symptomatic with any oscillopsia or do they have any abnormal head posture no matter how small or large this is.
64
Q

Examples of acquired nystagmus and their causes:

A
  • Upbeat = associated with brain stem lesions
  • Downbeat = result of cerebellar lesions
  • Abducting nystagmus = sign of internuclear ophthalmoplegia where the lesion is in the medial longitudinal fasciculus. They will also likely have limited adduction of the contralateral eye.
  • Monocular nystagmus = a result of spasmus newtons, or tumors of the optic chiasm or third ventricle.
  • Seesaw nystagmus = there is alternating elevation and in torsion of one eye and depression and extortion of the other eye which is as a result of chiasmal or parasellar mass lesions
  • Convergence retraction nystagmus syndrome – caused by parinaud’s/Dorsal midbrain syndrome
65
Q

Treatment acquired nystagmus:

A
  • Removal of cause may help e.g. Arnold Chiari – decompression foramen magnum
  • Drugs = can help dampen the nystagmus and lead to an improvement of their visual acuity
  • Surgery e.g. the modified test and brown procedure to shift null zone – variable success
  • Retrobulbar Botulinum Toxin injections – limited success Useful in non-ambulant patients

Binocular vision, visual impairment and paediatrics (6 decks)

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