Nystagmus Flashcards
What is Nystagmus?
A constant, involuntary oscillation of the eyes
What causes nystagmus?
Pathological or physiological
How many types of nystagmus are there?
45
What are the 3 categories of nystagmus?
- Physiological
2. Early‐onset 3. Acquired
What are the types of physiological nystagmus?
- Opto-kinetic (OKN) nystagmus:
Eye moves in response to a moving scene (train) - Vestibular (VOR) nystagmus:
Response to rotation of the body
-End point nystagmus: when looking in extreme positions of gaze
What is early onset nystagmus?
Presents within first few months of life
What are the types of early onset nystagmus?
Latent nystagmus, spasmus nutans and infantile nystagmus
What is latent nystagmus?
Either only appears when one eye is occluded (latent‐latent nystagmus) or worsens upon occlusion of one eye (manifest‐latent nystagmus).
What type of movement is seen in latent nystagmus?
Jerk and the beat direction is always towards the fixating eye. This means that covering the right eye will lead to jerk nystagmus, with both eyes jerking to the left
Switching occlusion to the left eye will reverse the beat direction, so that the eyes now jerk to the right
The eye movements follow Alexander’s law; i.e. when looking in the direction of the quick phase, nystagmus intensity increases
What is spasmus nutans?
Rare disorder along with head nodding and abnormal head posture
What is spasmus nutans caused by?
idiopathic
Does spasmus nutans recover?
Yes ceases spontaneously
What is infantile nystagmus?
A constant nystagmus, usually predominantly in the horizontal axis
When does infantile nystagmus start?
The condition develops within six months of birth, and persists throughout life
Not usually present at birth
What is infantile nystagmus caused by?
A visual system pathology or idiopathic
What are features of nystagmus?
Waveform Null zone Oscillopsia Psychological factors Head shaking Refractive error
What does waveform mean?
The pattern of eye movements seen
How many types of waveforms are there?
12
What are the 2 main types of waveforms?
Jerk and pendular
How can you clinically detect the specific type of waveform a nystagmus is?
High‐speed eye tracking
What is null zone?
A jerk nystagmus has a beat direction and if the patients turns their head to the direction of the beat then the nystagmus lessens- this is the null zone
How is the null zone helpful?
The patient will adopt a head posture at the null zone where nystagmus is minimised
What is Oscillopsia?
perception of the world moving back and forth
Who gets Oscillopsia?
Acquired nystagmus more likely to get it or if infantile nystagmus patient is unwell or tired they can also get it
What psychological factors affect nystagmus?
If px is stressed, it can intensify their nystagmus
Who gets head shaking?
27% of Infantile nystagmus
How does head shaking help?
Example:
As they move their head to the left, their eyes go to the right so can make it compensatory where the waveform is reduced
What sort of refractive error is seen in infantile nystagmus?
High refractive error due to poor emmetropization, more myopia
With the rule astigmatism
Astigmatism increases with age due to interaction between cornea and eyelids
What is acquired nystagmus caused by?
Disease or injury, often to the vestibular or central nervous systems
Common cause of acquired nystagmus?
MS or stroke
What are the features of a suspect acquired pathology are?
Asymmetry,
A significant vertical component to the nystagmus
Oscillopsia
Saccadic oscillations without any apparent slow phase
What questions do you ask in history taking in practice?
How long has nystagmus been present?
Is oscillopsia perceived?
Is there a history of strabismus?
Is there a family history of nystagmus?
Does nystagmus intensity increase with occlusion?
Is the movement symmetrical?
Does beat direction depend on which eye is covered?
Is head shaking present?
Does convergence cause dampening of nystagmus?
Is there a null zone? (Is a head posture used?)
How do you do tonometry for nystagmus patient?
Non contact tonometry is difficult so take extra care when doing contact
Take advantage of the patient’s null zone to dampen nystagmus as much as possible
How do you do refraction for nystagmus patient?
Phoropters should be avoided in favour of a trial frame, to allow patients to turn their head and view using the null zone
Wide‐aperture trial lenses are preferable although even this may not be sufficient for some patients to obtain the same quality of vision as with glazed spectacles or contact lenses.
Give patients plenty of time to respond
The use of a +10.00 DS lens for occlusion can help prevent increasing nystagmus intensity when measuring monocular VA in individuals with a latent nystagmus component
How do you do perimetry?
Using their null zone if available, but due to the constant eye movements, the results should be considered less sensitive to small field defects
What are you likely to see on cover test?
Strabismus is present in 64% of individuals with early‐onset nystagmus, with
98% of these cases being horizontal (esotropia or exotropia).
This is particularly the case in latent nystagmus, which is almost always accompanied by a history of squint. .
How do you manage nystagmus in primary practice?
Every child first presenting with a nystagmus= refer
Any change in nystagmus= refer
Acquired= urgent referral
