Introduction
Patients may notice abnormal movement of the visual world because of disease of the:
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inner ear
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brain
As ophthalmologists, we need to realize that serious disease can present with abnormal movement of the visual world and nystagmus. In general, nystagmus associated with oscillopsia is due to new-onset inner ear or brain pathology and requires urgent investigation. By contrast, patients who have nystagmus but do not notice the visual world moving have almost certainly had the nystagmus since early childhood (congenital sensory nystagmus due to blindness or congenital idiopathic nystagmus) (see Chapter 8 ).
We recommend that all patients with unexplained oscillopsia be evaluated by a neuro-ophthalmologist. If this is not possible, magnetic resonance imaging (MRI) brain with contrast is the necessary first investigation.
Inner ear disease
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probably the most common cause of nystagmus is vertigo due to inner ear diseases (e.g. an ear infection or Ménière disease). These conditions usually present to neurologists or ear specialists rather than to ophthalmologists. In contrast to brain causes of oscillopsia, the oscillopsia and nystagmus of inner ear disease are almost always transient and resolve within a week; there are also often other symptoms such as deafness or ear pain that help localize the disease
Brain disease
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most patients with nystagmus due to brain disease present to neurologists with multiple neurologic symptoms; an ophthalmologist is often only consulted once the cause has already been diagnosed on MRI and other tests. Occasionally, however, patients with acquired nystagmus present first to ophthalmologists complaining of “moving” or “jumping” vision
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brain disease can also cause the illusion of abnormal movement or orientation of the visual world with absolutely normal eye movements. Akinetopsia occurs when brain disease results in the loss of movement perception. Visual allesthesia due to brain disease results in the visual world being seen “tilted”
Types of eye movement disorders causing abnormal movement of the visual world
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this is a vast and complex topic, but most cases can be classified in a basic way as one of (or a combination of) the following:
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primary position nystagmus: the eyes are moving while the patient is looking straight ahead; due to inner ear, cerebellar or brainstem disease, medications or drugs
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jerk nystagmus (sidebeat, upbeat, downbeat) ( , and )
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pendular nystagmus ( )
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torsional (rotary) nystagmus ( )
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see-saw nystagmus ( )
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periodic alternating nystagmus ( )
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gaze-evoked nystagmus: the eyes are stationary with the patient looking straight ahead but start to move when the patient looks in other directions; due to cerebellar or brainstem disease, medications or drugs ( )
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superior oblique myokymia: the superior oblique muscle intermittently fires, causing intermittent oscillopsia and/or vertical diplopia; idiopathic or due to vascular compression of the fourth nerve root ( )
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saccadic intrusions: an unwanted and involuntary series of saccades disrupts fixation; due to a paraneoplastic syndrome or brain disease ( – )
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loss of the vestibulo-ocular reflex (VOR): the patient experiences “jumping” of the visual world when moving or walking due to loss of the usual VOR compensatory movements; due to cerebellar or brainstem disease
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Examination checklist
Abnormal movement of the visual world
Have you asked about, and looked for, all the following key features?
History
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the abnormal movement
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what does the patient notice? Does the world seem to move up and down, side-to-side or rotate around?
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does it seem to affect one or both eyes?
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when did it start?
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precipitating factors?
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does it happen at rest or only with head or body movement?
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does it occur only with the body or head in a particular position (e.g. lying on the right side)?
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constant or intermittent? If intermittent, how long do episodes last?
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getting better or worse or staying the same?
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any neurologic symptoms?
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deafness or tinnitus? (suspect vestibular schwannoma)
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problems with balance?
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headache?
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current or previous numbness, weakness, problems walking or talking?
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any other ophthalmic symptoms: blurred vision, double vision or field loss?
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previous medical and surgical history: cancer, atherosclerotic risk factors, medications (e.g. sedatives, lithium)?
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social history: smoker, alcohol, illicit drugs?
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if patient over 50: symptoms of giant cell arteritis (GCA)?
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system review questions: any clues to the cause anywhere in the body?
Examination
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visual acuity
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color vision testing
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visual field testing to confrontation
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eye movement testing
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are any abnormal ocular movements (e.g. nystagmus) visible in primary position or in other directions of gaze?
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are the eyes aligned in primary position?
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smooth pursuit testing of range of eye movement
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saccades: horizontal, then vertical
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convergence
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VOR (“doll’s-head”)
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pupils
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relative afferent pupillary defect (RAPD)?
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anisocoria?
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eyelids: ptosis?
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orbits
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decreased corneal or facial sensation to light touch?
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orbicularis or facial weakness?
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if patient over 50: palpate temporal arteries
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full neurologic examination: in all cases of unexplained oscillopsia
Plus: perform perimetry if:
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field defect to confrontation, or
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decreased visual acuity, color vision or RAPD
Oscillopsia
Definition
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an illusory to-and-fro movement of the environment
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may be horizontal, vertical, torsional or a combination of these directions
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usually caused by an acquired instability of fixation from vestibular or neurologic disorders
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when oscillopsia is produced or accentuated by head movement, it is usually of vestibular origin
Causes
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acquired nystagmus
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saccadic intrusions
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superior oblique myokymia
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abnormal VOR
Acquired nystagmus
Definition
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to-and-fro movement of the eyes
Types
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may be constant or intermittent: if intermittent, may occur only in certain directions of gaze or at near as opposed to distance
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may be pendular, jerk or mixed type
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pendular ( )
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movements in each direction are same amplitude and frequency
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patients describe to-and-fro movement of the world
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jerk ( and )
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frequency of movement in one direction (or phase) is faster than the frequency of movement in the other (fast phase versus slow phase)
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patients usually describe movement of the world in the direction of the fast phase
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although jerk nystagmus is described by the direction of the fast phase (e.g. downbeat nystagmus has a downward fast phase and an upward slow phase), it is the SLOW PHASE of the nystagmus that is the pathologic movement; the fast phase is a normal corrective movement
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Common types of acquired nystagmus
Central vestibular nystagmus
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downbeat ( )
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drug-induced (e.g. alcohol, anticonvulsants, lithium)
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Chiari malformation ( Fig. 7.1 )
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