DEMYSTIFYING NYSTAGMUS

DEMYSTIFYING NYSTAGMUS
Ms. ANJALI AHUJA,
M.Optom.
anjaliahuja008@gmail.com FINANCIAL DISCLOSURE NONE
Linkedin.com/in/anjali-ahuja-
9743ba9a
https://in-vision.org.uk/about-nystagmus/

• It comes from Greek words like “nustagmos” - drowsiness and “nystázein”- to drop off to
sleep.
• It can be described as regular, rhythmic, repetitive, to and fro, involuntary movements of
one or both eyes in either a fast or slow oscillatory motion.
NYSTAGMUS
Horizontal
Nystagmus – EyeWiki and Gif: https://in-vision.org.uk/about-nystagmus/
Vertical Torsional Combination

EPIDEMIOLOGY
• The prevalence of pathologic nystagmus is estimated to be 24 per 10,000 with a slight predilection toward
European ancestry. The prevalence of infantile/pediatric nystagmus is said to be 17 per 10,000.
• The frequency of acquired nystagmus is estimated at 17% in children in contrast to 40% in adults.
Clinical diagnosis and frequency distribution of patients with nystagmus
The numbers beside the bars represent
prevalence per 10,000 (±95% CI), calculated
separately for the 18 years or younger and
older than 18 years age groups.
Sarvananthan N, Surendran M, Roberts EO, Jain S, Thomas S, Shah N, et al. The prevalence of nystagmus: the Leicestershire nystagmus survey.
Invest Ophthalmol Vis Sci, 50 (2009), pp. 5201-5206

AIM OF OCULAR MOVEMENTS
• There are three main control mechanisms for maintaining steady gaze:-
a) Fixation
b) Vestibulo-ocular reflex
c) A gaze-holding system (the neural integrator)
• Failure of any of these control systems will bring about a disruption of steady fixation.
• Two types of abnormal fixation can result:-
i. Nystagmus
ii. Saccadic intrusions/oscillations
• The essential difference between them lies in the initial movement that takes the line of sight off the object
of regard.
• In the case of nystagmus, it is a slow drift or ‘slow phase’ that moves eyes off target
• On the other hand, with either saccadic intrusions or saccadic oscillations, it is an inappropriate fast
movement that moves the eyes off target.
Richard V Abadi Mechanisms underlying nystagmus J R Soc Med. 2002 May; 95(5): 231–234. doi: 10.1258/jrsm.95.5.231

MECHANISM UNDERLYING NYSTAGMUS
• During times of an imbalance, such as in unilateral
vestibular loss, the eyes are ‘pushed’ to the affected
side by the opposite ‘uninhibited labyrinth’.
• However, the brainstem keeps this normal/unaffected
labyrinth in check and rapidly ‘turns’ the eyes back to
the normal side.
• This constant repetitive cyclic struggle between the
labyrinth and brainstem results in a movement of the
eyes termed as nystagmus.
• Normally, this nystagmus persists until the underlying
vestibular loss is ether cured, or taken care of by
compensation.
• The two phases of nystagmus are; the ‘slow phase’,
due to the abnormality in the vestibular system; and
the ‘fast phase’, due to the corrective central
mechanism.
Hathiram BT, Khattar VS. Nystagmus. Otorhinolaryngol Clin Int J 2012;4(2):93-99.

CLINICAL TERMINOLOGY
• If the second movement is slow, the nystagmus is said to be pendular. It has smooth sinusoidal oscillation,
equal on both sides.
• If this second movement is quick, the nystagmus is called jerk nystagmus. It has slow component and fast
component.
1) TYPES:-
2) WAVEFORMS:-
• The nystagmus waveform represents the position of the eye over
time, and it is obtained by performing eye movement recordings.
• Nystagmus waveforms are named for their slow phase velocity
profile.
• The pendular form has no fast phase and is best depicted by the
first wave. The exponential increasing velocity type is associated
with congenital nystagmus. The exponential decreasing velocity
waveform is seen in gaze-evoked nystagmus, which can be a
physiologic finding. The linear waveform is typical of vestibular.
Hanson KS, Bedell HE, White JM, Ukwade MT. Distance and near visual acuity in infantile nystagmus. Optom Vis Sci. 2006;83(11):823–829.

3) AMPLITUDE:-
• It is the excursion of the nystagmus and is described as small or fine (less than 5°), moderate (5°-15°) and
large (greater than 15°).
4) FREQUENCY:-
• It is the number of to and fro movements in one second. It is described in cycles per second or Hertz (Hz).
• It is slow (1-2 Hz), medium (3-4 Hz) or fast (5Hz or more).
4) INTENSITY:-
• It is calculated by multiplying the nystagmus amplitude by the frequency, thus representing the average
velocity of the eye movements.
4) ALEXANDER’S LAW:-
• It states that the amplitude of jerk nystagmus is largest in the gaze of the direction of fast component.
• Based on this principle three degrees of nystagmus are described:-
First – Nystagmus only in the gaze in the direction of fast component.
Second – Nystagmus also in primary position gaze.
Third – Nystagmus in addition of above two is also present in the direction of slow component.
Sharma P, Strabismus Simplified, 2nd edition, CBS Publishers, New Delhi 2013

4) NULL ZONE:-
• The field of gaze in which nystagmus intensity is minimal is termed the "null zone”.
CHAPTER 11, Ocular Motor Neurophysiology Laboratory,
Veterans Administration Medical Center, Cleveland, Ohio
4) DISSOCIATED NYSTAGMUS:-
• It refers to the two eyes having nystagmus with the same direction but with differing amplitudes.
4) DISCONJUGATE NYSTAGMUS:-
• It refers to the two eyes have different directions of oscillation, one example of which is
sea-saw nystagmus.
• It presents as oscillations in which one eye elevates and intorts (rotates towards the nose)
while the other eye depresses and extorts (rotates away from the nose).
• These oscillations usually have a pendular waveform but can sometimes have a jerk
waveform. It can be congenital or acquired.
4) PERIODIC ALTERNATING NYSTAGMUS:-
• It characterized by a cycle of unidirectional jerk nystagmus followed by a dampening or
cessation of the abnormal eye movement, then jerk nystagmus occurring in the opposite
direction.
• In order to observe PAN, the examiner should consider observing the patient for at least
several minutes. Each full PAN cycle taking approximately 3-4 minutes.

NYSTAGMUS
PHYSIOLOGIC
NYSTAGMUS
PATHOLOGIC
NYSTAGMUS
CLASSIFICATION
Sharma P, Strabismus Simplified, 2nd edition, CBS Publishers, New Delhi 2013

(A) PHYSIOLOGIC NYSTAGMUS
1) END – POINT NYSTAGMUS
• End point nystagmus occurs when the eyes are
forced to move to the extreme far point of their
lateral (sideways) movement.
• This results in an oscillation of the eyes which
will disappear if the extremity of the gaze is
reduced.
• End-point nystagmus is chiefly caused by the
shortcomings of the human 'neural integrator'.
2) VESTIBULAR NYSTAGMUS
• VOR is the reflexive movement of the eye that
keeps the visual image stable on the retina during
brief, high frequency rotation of the head.
• Rotation of the head causes movement of the fluid
within the semi-circular canals of the inner ear.
• VORs are controlled by the vestibular system of the
inner ears, namely the semicircular canals, utricle,
and saccule.
Nystagmus – EyeWiki and https://in-vision.org.uk/about-nystagmus/

3) CALORIC NYSTAGMUS
• It is a type of VOR (vestibulo-ocular
reflex) that is elicited by stimulating
the horizontal semicircle with either
warm or cold water in the ear canal to
create a convection current in
the endolymph of the semicircle.
• In normal subjects, when cold water
is placed in one ear, the eyes will
slowly turn toward the ear with the
horizontal fast phase away from the
ear.
• The absence of caloric nystagmus may
indicate brain death.
4) OPOTOKINETIC NYSTAGMUS
• OKN is a physiologic movement of the eyes in response to large,
moving visual fields (e.g. when one is looking out the window of
a moving train).
• The initial movement is a smooth pursuit movement followed by
contraversive saccade back to primary gaze or direction of visual
interest.
• The use of an optokinetic drum gives an approximation of OKN in
action. Asymmetry of the OKN response to the rotating drum
may suggest lesions of the cerebrum, typically a large lesion of the
parietal or parieto-occipital cortex and associated with
homonymous hemianopia.
• This is in contrast to the lesions of the occipital lobe which also
produce homonymous hemianopia but without the OKN
asymmetry.

(B) PATHOLOGIC NYSTAGMUS
• The classification of eye movement abnormalities and strabismus (CEMAS) group have recommended
new names for nystagmus that begins during infancy. Three categories have been defined:-
1) Infantile Nystagmus Syndrome (Childhood Nystagmus):-
• It is also known as congenital motor nystagmus, is the most common type of nystagmus seen in young
patients followed by congenital sensory nystagmus.
• It is by definition idiopathic (e.g. without a known cause or associated afferent pathway disease) and is
therefore a diagnosis of exclusion.
• It is present from infancy but usually recognized a few months into lifeand may even be evident only after
the child has reached several years of age.
• It is almost always bilateral, conjugate, and occurs in the horizontal plane, even in upgaze and downgaze,
with little variability. Both jerk and pendular types are seen.
• In 2006, Tarpey et al. discovered the first gene causing INS —the FRMD7 gene—so obtaining history and
examining family members may be of yield.
Nystagmus – EyeWiki

• Two additional important signs of IIN are:-
- Reversal of normal optokinetic nystagmus upon presentation of the rotating OKN drum
- Exponential increase of slow phase eye movement
• The visual acuity is proportional to the foveation time, and in most patients, the visual acuity is at or greater than
6/12.

2) Fusional Maldevelopment Nystagmus Syndrome (Latent Nystagmus) :-
• It is a conjugate, horizontal jerk nystagmus and a marker of fusion maldevelopment, which occurs as a result of
infantile- onset strabismus or decreased vision in 1 eye.
• When either eye is occluded, a conjugate jerk nystagmus develops, with the direction of the fast phase component
toward the uncovered eye.
• Left jerk nystagmus occurs upon covering the right eye, and right jerk nystagmus upon covering the left.
• This is the only nystagmus that reverses direction depending on which eye is fixating. The nystagmus damps when the
fixating eye is in adduction, so the preferred head turn also reverses direction with change of fixation (Fig).
• Amplitude, frequency, and velocity of the nystagmus can also vary depending on which eye is fixating.

3) Spasmus nutans :-
• It is classically characterized by the triad of binocular small-amplitude pendular nystagmus, head
nodding, and abnormal head posture or torticollis manifesting itself in the first year of life.
• Some authors suggest that the head nodding in SN is a compensatory mechanism
for oscillopsia rather than a separate pathological manifestation.
• Spasmus nutans in itself is a relatively benign condition that resolves by the end of the first decade
of life though with often reduced visual acuity with or without significant refractive error.
• The pendular nystagmus of SN is notable in that it is highly variable in amplitude and phase
direction--at times becoming disconjugate, dissociated, purely monocular, then to conjugate over
the course of minutes.
• The markedly asymmetric and sometimes monocular involvement of SN may be indistinguishable
from the possibly life-threatening manifestations of optic pathway gliomas that cause monocular
nystagmus of childhood.
• Neuroimaging should be considered.
• Some authors reported the association between retinal dystrophies and suggested
that electroretinographic studies be considered to assess for such disorders in patients presenting
with suspected SN.

Sensory Nystagmus :-
• It also known as nystagmus associated with afferent visual system abnormalities, is usually seen in the first
3-4 months and has the same oculomotor features as infantile nystagmus, but is due to anatomic disorders
of the eye that, by limiting the proper visual sensory input to the eye, limit the visual development of the
patient.
• The causes of sensory nystagmus are many—but a few common etiologies can be remembered by the 5 A’s
mnemonic:
1. Aplasia (hypoplasia) of the optic nerve (optic nerve hypoplasia),
2. Leber congenital amaurosis,
3. aniridia,
4. Achromatopsia, and
5. ocular albinism.
• Other causes include impairment of the cortical system as seen in preterm infants with periventricular
leukomalacia and those with traumatic brain injury or metabolic disorders.
• These entities must be ruled out in patients undergoing evaluation of their nystagmus by searching for
impairment of visual tracking and optic atrophy.
• Neuroimaging may be recommended.

Monocular nystagmus of childhood:-
• Monocular nystagmus of childhood is nystagmus that involves the same eye at all times in a child.
• The waveforms have small amplitudes and can be vertical or elliptical.
• Heimann-Bielschowsky phenomenon is a type of monocular nystagmus that occurs due to longstanding poor vision in
one eye with amblyopia, optic neuropathy, or dense cataract.
• It can often be inhibited by convergence or fixation.
• There are reports of improved monocular nystagmus after extraocular muscle surgery in the case of strabismic
amblyopia causing the Heiman-Bielschowsky phenomenon.
• When an infant presents with signs of afferent pathway disease (e.g. optic disc atrophy, relative afferent pupillary
defect, and monocular nystagmus) neuroimaging should be considered.
• MRI figure shows an example of a child who presented with monocular nystagmus and a chiasmic-hypothalamic mass.

Acquired nystagmus :-
Nystagmus is considered to be acquired in patients presenting at or after the age of 6
months especially with asymmetric nystagmus (one eye with greater amplitude and/or
frequency than the fellow eye), preservation of optokinetic nystagmus, presence of a
relative afferent pupillary defect, papilledema, or neurologic signs or symptoms.
1) Gaze evoked nystagmus:-
• Gaze evoked nystagmus appears as jerk nystagmus induced upon deviation of the eyes
away from the primary position (straight-ahead).
• In the primary position the usual presentation is of unsteady fixation but sometimes
pendular nystagmus can also be observed.
• In lateral gaze positions a horizontal nystagmus will appear; in upgaze, upbeat nystagmus
may appear, but with a smaller intensity than the horizontal nystagmus. A downbeat
nystagmus in downgaze can also be present but is much less common.
• In the oblique gaze positions an oblique nystagmus can occur but if the vertical gaze-
holding circuitry of the visual system is unaffected then the nystagmus will be purely
horizontal.
• Gaze evoked nystagmus can be differentiated from FMNS by the absence of any change in
the oscillations following the occlusion of one eye.
• Gaze evoked nystagmus can be caused by cerebellar disorders or follow the use of
sedatives, anticonvulsants, alcohol, cannabis, barbiturates, diazepam or chloral hydrate.

2) Rebound nystagmus:-
• It is a characteristic of gaze evoked nystagmus that is seen when the subject is
asked to maintain an extreme lateral gaze position.
• In this situation the horizontal nystagmus intensity gradually decreases and
sometimes even reverses its direction.
• If this is followed by a rapid return to the primary position, then the brief rebound
nystagmus occurs.
• The rebound nystagmus lasts for only a short time and beats away from the
direction of the maintained lateral gaze.
• Rebound nystagmus can sometimes be observed in subjects who also show end-
point nystagmus.

3) Downbeat nystagmus:-
• It is the most common of the central vestibular nystagmus.
• Its jerk nystagmus waveform begins with upward drift of the eyes corrected with a downward saccade.
• This form of nystagmus follows Alexander's Law and hence is accentuated by downgaze and also by
lateral-down gaze, but is also amplified by convergence and lying prone.
• Generally, patients are symptomatic from vertical oscillopsia.
• The differential for down-beating nystagmus is broad, but structural lesions can be ruled out with
neuroimaging. Cervico-medullary junction is the most probable location of a structural lesion.
• Tumors at the foramen magnum, Arnold-Chiari malformation Type I, Demyelination, Stroke, Cranial trauma are
common findings.
• There are several antibodies that have been associated with downbeat nystagmus in a growing number of
cases, mainly antibodies to voltage gated calcium channels and to glutamic acid decarboxylase (GAD).

4) Upbeat nystagmus:-
• It is purely-vertical conjugate nystagmus that manifests itself in primary gaze
with slow down drift of the eyes corrected by fast upward saccade.
• Patients may experience vertical oscillopsia.
• Structural lesions in the brainstem or in the anterior cerebellar vermis can
cause this type of nystagmus.
• Causes include demyelinating disease, stroke, tumors, cerebellar
degeneration, and tobacco smoking.

CLINICAL EXAMINATION
• When assessing a patient with nystagmus, the examiner should consider assessing ocular stability/motility in primary
gaze first followed by observation of the eye movement in cardinal gazes.
• A full description of the nystagmus should be gathered from examination, concisely presented in the form of the
mnemonic DWARF—Direction, Waveform, Amplitude, Reducing direction, Frequency. In addition, the following
characteristics should be identified:
1. Monocular or binocular involvement
2. Conjugacy (do both eyes move together?)
3. Direction of movement (horizontal, vertical, torsional, or mixed)
4. Stability of direction of movement (is the phase gaze always to the right?)
5. Continuous or intermittent
6. Amplitude (how big are the movements?)
7. Frequency (how often are the movements happening?)
8. Presence of null point (the direction of gaze or distance of fixation at which nystagmus is minimal to nil)
9. Presence of slow phase (if there is no slow phase, the eye movement disorder is considered a saccadic intrusion)
10. General condition of the patient (is the patient comatose?)
11. Associated symptoms such as vertigo, nausea, and oscillopsia

Electrophysiological examination
• Electronystagmography: Eye movement recordings allow accurate
classification of the nystagmus waveform.
• These types of examination techniques are rarely available but can be
useful, for instance, the determination of normal electroretinography and
pattern visual evoked potentials is an indication of an INS.
• Abnormal results in these electrophysiological tests can reveal less
obvious sensory defects that may be present or identify a neurological
abnormality.

• Nystagmus is frequently a sign of an underlying pathologic process. Thus, proper care of the nystagmus
patient requires that any fundamental pathologic process be properly diagnosed and treated.
• Management is directed at reducing the manifestations of nystagmus by improving visual acuity and
enhancing binocularity.
• Management that can improve nystagmus includes optical measures such as:-
(a) use of refractive correction
(b) added lenses
(c) prism
• Vision therapy procedures and certain medications can assist development of nystagmus control.
• Finally, ocular muscle surgery will help in selected cases by aligning the eyes, lessening the nystagmus,
improving function through an expanded relative null (which allows clearer vision over a wider area of the
field without a head turn), and reducing head turn.
MANAGEMENT
Scheiman W, Clinical management of Binocular Vision, 4th edition, Wolters Kluwer Publishers.

• Because the quality of the retinal image can directly influence the ability to maintain accurate steady
fixation, the importance of correcting significant refractive error in the management of nystagmus should
not be taken lightly.
• When refractive treatment is necessary: greater than 1 to 2 D of hyperopia, 0.50 D or more of astigmatism,
or 0.50 D or more of myopia or anisometropia.
• These amounts are often clinically significant, and optical correction should be the first consideration in
management.
• For some patients, rigid gas-permeable contact lenses have been reported to result in greater control of
the nystagmus intensity immediately upon insertion and also over time. This effect may be attributable to
two factors.
• First, there is often undetected astigmatism associated with congenital nystagmus. In these cases, the
contact lens gives a clearer retinal image, thereby potentially reducing the nystagmus.
• Second, as the eyes move, the lenses may cause lid sensations and give feedback information that allows
control to be developed.
• Soft contact lenses probably do not have the same feedback effects but are often preferred for correction
of significant refractive errors, such as those occurring after removal of congenital cataracts.
REFRACTIVE CORRECTION

1) PLUS ADDS :-
• Added plus can be very useful when there is reduced visual acuity and demanding near
tasks.
• Young patients usually hold near work close and use relative magnification to read print
of the size required for adequate school performance.
• However, they often need a near addition to assist them in maintaining accommodation
as they get further along in school, where more prolonged studying is required.
• Older patients, who are losing accommodation, and all patients with very poor acuity
may need near additions that are somewhat stronger than normal, especially when
significant magnification is needed to improve near acuity.
ADDED LENSES

2) MINUS ADDS :-
• It is well known that some patients with nystagmus have decreased nystagmus
with convergence.
• Thus, some clinicians have suggested the use of added minus lenses that are
weaker than the refractive correction in an attempt to lessen the effects of
nystagmus.
• The theory is that the minus power puts a patient into a converged position.
• In the presence of strabismus and a moderate or high AC/A ratio, a significant
change in convergence posture is often possible by making a patient
accommodate through added minus lenses.

PRISM CORRECTION
• Prism corrections to lessen the nystagmus probably work by inducing convergence or placing the eyes in the
null position.
• When the intensity of nystagmus decreases with convergence, the effect of base-out prisms on nystagmus
intensity should be tested.
• In these cases, small to moderate amounts of base-out prism will often decrease the nystagmus, with a
resulting improvement in acuity.
• The amount of prism required varies considerably from patient to patient. The total amount, which is typically
determined empirically, generally ranges between 10 and 20 Δ base-out.
• Fresnel prisms are often used for higher prescriptions.
• Prism can be prescribed with the bases in the same direction (yoked or conjugate prism) of nystagmus as a
method of improving visual acuity or of treating the abnormal head postures that are often associated with
nystagmus.
• Fresnel prisms are available in amounts up to 30 Δ to manage moderate face turns, but acuity is somewhat
degraded with the higher powers.

VISION THERAPY
• Antisuppression Therapy:-
- A frequent clinical observation regarding the intensity of nystagmus is that it lessens as binocular vision is
enhanced.
- Thus, an important initial step in therapy for heterophoria patients with nystagmus is treatment of
suppression.
- Suppression training uses active therapy, including Polaroid or anaglyphic TV trainers, anaglyphic coloring
activities, and tranaglyphs or vectograms.
- Active treatment involves binocular (dichoptic) stimulation of peripheral retinal areas followed by gradual
encroachment upon central areas.
- Attention is drawn to simultaneous perception of suppression clues and clearness of the clues seen by each
eye.
- Finally, physiologic and pathologic diplopia therapy are added.
- Sensory fusion should be maximally developed before motor fusion therapy begins.

PHARMACOLOGICAL TREATMENT
• For the treatment of congenital nystagmus (both in idiopathic and secondary
forms), pharmacologic therapies with gabapentin and memantine have been
studied in a randomized clinical trials of adult patients.
• Statistically significant improvement in visual acuity and nystagmus amplitude
were measured in patients in the treatment arm compared to those in the
placebo arm.
• Trials of botulinum toxin injection into the retrobulbar space have been done to
treat symptomatic nystagmus.
• While some patients reported improvement in oscillopsia, side effects including
ptosis, diplopia, and paradoxical worsening of oscillopsia due to limitation of
VOR have limited the utility of botulinum toxin as a treatment option.

SURGERY
• Extraocular muscle surgery as a treatment for nystagmus is mostly for infantile
nystagmus.
• The Anderson-Kestenbaum procedure mechanically shifts the null point from a
horizontal cardinal position to primary position.
• An equivalent procedure may be performed for patients with vertical nystagmus.
• More recently, four-muscle tenotomy and reattachment without transposition has
been found to be effective as well.
• A case of a pilot, experimental intervention using magnetic oculomotor prosthesis
has also been reported with objective improvement of visual acuity and reduction
of acquired nystagmus.

DEMYSTIFYING NYSTAGMUS

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to DEMYSTIFYING NYSTAGMUS

Similar to DEMYSTIFYING NYSTAGMUS (20)

More from Mero Eye

More from Mero Eye (20)

Recently uploaded

Recently uploaded (20)

DEMYSTIFYING NYSTAGMUS