Nystagmus Flashcards
What is nystagmus:
Rhythmic, repetitive and involuntary movement of eyes up down, side to side or circular motion
Features of nystagmus:
- 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
Classification of nystagmus:
- Physiological
- Pathological
- Infantile / Congenital
- Acquired
What are the 4 types of physiological nystagmus:
- Opto-kinetic (OKN)
○ Response to a moving scene (train)
○ A nystagmus induced by looking at moving visual stimuli. - Vestibular (VOR)
○ Response to rotation of the head (light and dark)
○ Alternating smooth pursuits in one direction and saccadic movements in the other direction - End point
○ In extreme lateral gaze - Voluntary
○ 5% of the normal population
Example of pathological nystagmus:
Benign congenital idiopathic nystagmus
What is pathological nystagmus the result of:
Damage to one or more components of the vestibular system E.G. semicircular canals, otolith organs, and the vestibular cerebellum.
What does pathological nystagmus cause:
Visual impairment
What can congenital idiopathic nystagmus be secondary to:
- 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
How are optokinetic i.e pendular and vertibular i.e jerk nystagmus revealed:
- By electronystagmography
- Only revealed by carrying out eye movement recordings.
What is jerk nystagmus:
- 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
What is pendular nystagmus:
- No fast phase - sinusoidal
- Can occur in any direction, torsional, horizontal, vertical, or even a combination of these.
- Smooth oscillations
What are the commonest types of nystagmus waveforms:
- Pendula
- Pendula with foveating saccades
- Pseudo-cylcoid
- Jerk with extended foveation
- Jerk nystagmus
What is the direction of beating of the nystagmus defined by:
The direction of the fast phase of the movement.
What are the features of waveforms in nystagmus:
- May be a combination of jerk/pendular nystagmus
- May vary with gaze direction
- Can be complex!
What is amplitude:
The ‘excursion’ of the nystagmus
What is frequency:
Number of oscillations per minute - ‘coarse, medium or fine’
What is intensity:
Amplitude x frequency
What is manifest nystagmus:
Present when both eyes are open but may increase when one eye is covered
What is latent nystagmus:
- 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
When is congenital nystagmus usually present from:
Around two to six months of age.
What are the two primary forms of congenital nystagmus:
- Sensory deficits nystagmus
- Congenital idiopathic nystagmus.
- It is not possible to differentiate between these two forms purely from a clinical observation of their nystagmus.
Aetiology/cause of congenital idiopathic nystagmus:
- The cause is most likely unknown.
- There is some suggestions that it could be X-linked, autosomal dominant or even sporadic.
Aetiology/cause of sensory deficits nystagmus:
- 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.
How is manifest latent nystagmus different from manifest latent nystagmus:
Separate diagnosis
What is manifest latent nystagmus associated with:
Early Onset Strabismus & DVD
When is manifest latent nystagmus detected:
Around 2 years of age
When is manifest latent nystagmus worsened:
If 1 eye is occluded and in abducted position of gaze
Describe the waveform in congenital nystagmus:
- 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.
Direction of congenital nystagmus:
- 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.
What does null zone mean in nystagmus:
The direction of gaze in which the eyes of someone with nystagmus are most stable. And therefore the vision is at its best
Features of null zone:
- 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
Assessing VA in patients who have any form of nystagmus:
- 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)
VA in congenital idiopathic nystagmus vs sensory deficits nystagmus:
- 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
What does it mean if px with nystagmus has a significant abnormal head posture:
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.
Testing near vision in px’s with nystagmus:
Test at patient’s preferred distance
What would we need to record for when testing near vision in px’s with nystagmus:
- 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
What can px’s with congenital idiopathic nystagmus achieve for near vision testing:
N5
Other features of congenital nystagmus:
- Nystagmus usually similar in both eyes
- May increase on occlusion of one eye
- May be associated with strabismus
What is present in some px’s with congenital nystagmus:
Head nodding - but usually disappear over time
What can head bobbing and torticollis be:
Compensatory mechanisms that improve vision by reducing the frequency and asymmetry of the nystagmus
What is spasm nutans:
- 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.
When do px’s complain of oscillopsia:
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
What is complaints of oscillopsia suggestive of:
Acquired or voluntary nystagmus
What is voluntary nystagmus:
- 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.
Management of nystagmus:
- 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
What is the management of congenital nystagmus:
- 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
Treatment options for nystagmus px’s:
- Glasses / Contact lenses
- Low vision aids
- Prisms
- Drugs
- Botulinum Toxin
- Surgical corrections of eye movements
Refractive correction treatment for nystagmus px’s:
- Glasses if find any underlying refractive error – to ensure best possible corrected vision
- Contact lenses – move with the eye therefore ensures best corrected vision.
Low vision aids treatment for nystagmus px’s:
- 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
How successful are prisms in px’s with nystagmus:
Prisms have a limited success rates in patients with nystagmus, especially if their null zone is in the extreme positions of gaze.
Treatment of prisms for px’s with nystagmus:
Temporary Fresnel prisms can be given in the first instance, which are applied to their glasses and can be incorporated into their glasses
How do prisms help px’s with nystagmus - example:
- 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.
Drugs used for management of treatments of acquired nystagmus:
- 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
Botulinum Toxin injections:
- 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
Treatment to reduce abnormal head posture:
- 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.
When is surgery option:
Some centers offer eye surgery to children and adults with nystagmus where there is a marked head-turn due to a null point.
Surgery for px’s with nystagmus where there is a marked head-turn due to a null point:
- 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
How effective is nystagmus surgery:
Nystagmus surgery aims to reduce the amplitude of nystagmus with either improvements of visual acuity or a reduction of bothersome head posture.
What is the most common reason for patients seeking surgical treatment for nystagmus:
To allow them to acquire a driving license.
What is the principle underlying surgical treatment for nystagmus:
- 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.
Other treatment for congenital nystagmus:
- 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
How is acquired nystagmus different from congenital nystagmus:
- Different clinical characteristics from congenital nystagmus
- Usually represents intracranial pathology (e.g. multiple sclerosis, CVA, tumours, head trauma)
- Presents with known onset and oscillopsia
Differential diagnosis - congenital/acquired:
- 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.
Examples of acquired nystagmus and their causes:
- 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
Treatment acquired nystagmus:
- 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
