2. Defination
Nystagmus is a regular,repetitive to and fro
movement of the eyes (horizontal,vertical or
torsional) with 2 phases
1. slow drift from the target of interest f/b
2. corrective saccade back to the target
4. Amplitude
Amplitude is the excursion of the nystagmus and
described as
Fine : less than 50
Moderate: 50-150
Large greater than 150
5. Frequency
Frequency is the number of to and fro movements in
one second
Described an cycles/sec or Hertz (Hz)
Slow : (1-2 Hz)
Medium : (3-4 Hz)
Fast: (5 Hz or more)
6. Intensity
Intensity = amplitude * frequency
Null zone: position where nystagmus is minimised
Patient assumes a head posture, such that the eyes are
in null zone
7. Pursuit /Saccade
Pursuit eye movements allow the eyes to closely
follow a moving object.
Pursuit differs from the vestibulo-ocular reflex, which
only occurs during movements of the head and serves
to stabilize gaze on a stationary object
Saccades are quick, simultaneous movements of both
eyes in the same direction
8. Conjugate/Dissociated
Conjugate : nystagmus which is symmetric in
direction,amplitude and rate
Dissociated: when it differs in any one of the
parameters between two eyes
9. Jerk / Pendular
Jerk nystagmus Pendular nystagmus
Alternation of slow phase drift f/b rapid
corrective saccade in opp direction
Sinusoidal oscillation with slow phase
in both directions and no corrective
saccade
Direction of jerk nystagmus= direction
of the fast phase
Pendular nystagmus may be horizontal
or vertical
Right or left beating nystagmus
Upbeat or downbeat nystagmus
Not characterised by right,left,up,down
beating as there is no fast phase
10.
11. Alexanders law
It states that the amplitude of jerk nystagmus is
largest in the gaze of direction of fast component
1 degree: nystagmus only in the direction of the fast
component
2 degree: nystagmus in primary gaze position
3 degree: nystagmus in addition to above gazes,also
present in the direction of the slow component
12. Mechanism of nystagmus
Foveal centration of an object of regard is necessary to
obtain the highest level of visual acuity
Three mechanisms are involved in maintaining foveal
centration of an object of interest:
Fixation
The vestibulo-ocular reflex
The neural integrator.
13. Fixation
Fixation in the primary position involves the visual
system's ability to detect drift of a foveating image
and signal an appropriate corrective eye movement to
refoveate the image of regard.
The vestibular system is intimately and complexly
involved with the oculomotor system
14. Vestibulo-ocular reflex
The vestibulo-ocular reflex is a complex system of
neural interconnections that maintains foveation of
an object during changes in head position.
The proprioceptors of the vestibular system are the
semicircular canals of the inner ear.
The semicircular canals respond to changes in
angular acceleration due to head rotation
15. Neural integrator
When the eye is turned in an extreme position in the
orbit, the fascia and ligaments that suspend the eye
exert an elastic force to return toward the primary
position
To overcome this force, a tonic contraction of the
extraocular muscles is required.
A gaze-holding network called the neural integrator
generates the signal. The cerebellum, ascending
vestibular pathways, and oculomotor nuclei are
important components of the neural integrator.
18. Characteristics
Horizontal nystagmus ( mixed pendular and jerk)
b/l conjugate movements of the eyes
Nystagmus not present during sleep
Associated latent nystagmus
Head turn to achieve null point
Decreases with convergence
Increases with fixation
19. Reverse response to OKN stimulus ( fast phase in
direction of moving OKN drum)
May be seen in isolation or associated with
strabismus,afferent visual defects
20. Treatment
Base out prisms to induce convergence ( dampens the
nystagmus and may improve visual acuity)
Use of prisms to shift the viewing position to null
position
Contact lenses may dampen nystagmus
Gabapentine may dampen nystagmus
21. Surgical
Includes moving the extraocular muscles to place the
null zone in primary position(kestenbaum procedure)
Recessing all 4 rectus muscles to decrease tension
(large recession procedure)
22. Spasmus nutans
Triad of symptoms:
Nystagmus
Head nodding
Torticollis (head tilt or head turn)
23. Onset usually in the first year of life (3-15 months)
Disappears by 3-4 yrs of age
The nystagmus typically consists of small-amplitude,
high frequency oscillations and usually is bilateral,
but it can be monocular, asymmetric, and variable in
different positions of gaze
Usually benign
Neuroimaging recommended ( gliomas may mimic
spasmus nutans)
24. Infantile monocular pendular
nystagmus
Usually due to visual loss( often optic neuropathy or
chiasmal glioma)
In cases of b/l visual loss,there is b/l nystagmus ,with
nystagmus greater in eye with poorest vision
26. End point nystagmus
Jerk nystagmus
On looking extreme lateral or upwards
Angle of gaze > 450
27. Vestibular nystagmus
Jerk nystagmus
Altered inputs from vestibular nuclei to PPRF
Demonstrated by caloric test: normal response
Cold water : opposite side
Warm water : same side
Cold water in both ears: upwards
Warm water in both ears : downwards
28. Optokinetic nystagmus
Jerk nystagmus
Induced by moving a full visual field stimulus
Slow phase (pursuit) : eye follows the target
Fast phase ( saccade): eye fixates on next target
Uses: Detecting malingering
Testing visual potential in children
33. Gaze paretic nystagmus
Most common type
Absent in primary position and is not visually
disabling
Beats in the direction of gaze
Causes: anticonvulsants
brainstem lesions
cerebellar lesions
34.
35. Convergence-retraction
nystagmus
Not truly a nystagmus
b/l adducting saccades causing convergence of both
eyes
Elicited by having the patient to look up,at which
time the eyes converge & retract
Causes: midbrain lesions
36.
37. Vestibular nystagmus
Feature Peripheral Central
Disease of vestibular
origin
Disease of the brainstem
Direction Intensity increases when
the eyes are turned in
direction of fast phase
Direction of nystagmus
may change with gaze
Visual fixation Inhibits nystagmus No inhibition
Severity of vertigo Severe Mild
Induced by head
movements
Often Rare
Associated eye movement
deficits
None Pursuit or saccadic
defects
Other findings Hearing loss CNS involvement
38. Upbeat nystagmus
Type of jerk nystagmus with fast phase upward in
primary position
Often worsens in upgaze
Causes: lesions of medulla,
cerebellar vermis,midbrain
Rx: base up prisms in reading glasses can be used to
force the eyes downward
39.
40. Downbeat nystagmus
Type of jerk nystagmus with fast phase downward in
primary position
Often worsens in downgaze
Oscillopsia is usually prominent
Causes: lesions at cervicomedullary junction
Rx: base down prisms in reading glasses can be used
to force the eyes upward
41.
42. Seesaw nystagmus
Defined as pendular nystagmus with elevation and
intorsion of one eye simultaneous with depression
and extorsion of other eye
Followed by reversal of cycle,so that the eyes move
like a seesaw
43. Causes: parasellar lesions,pituitary tumors
Produces very disabling oscillopsia that responds
poorly to any Rx
44. Periodic alternating
nystagmus(PAN)
PAN is a conjugate, horizontal jerk nystagmus with
the fast phase beating in one direction for a period of
approximately 1-2 minutes.
The nystagmus has an intervening neutral phase
lasting 10-20 seconds
The nystagmus begins to beat in the opposite
direction for 1-2 minutes then, the process repeats
itself
45. Periodic alternating head turn to minimise nystagmus
& oscillopsia
Causes: lesions of the cerebellum
46.
47. Acquired Congenital
Form Pure sinusoidal Variable waveform
Direction Omnidirectional
(vertical,torsional)
Horizontal,uniplanar
Rarely vertical or
torsional
OKN reversal Never Frequent
Oscillopsia Frequent Mild (if present)
49. Manifest nystagmus Manifest-latent nystagmus
Pendular nystagmus Jerk nystagmus
No change on abduction Increased on abduction
No change on covering one eye Increase on covering one eye
Null zone is present Fast phase always towards fixing eye
Less commonly associated with
infantile esotropia
Always associated with esotropia
Binocular visual acuity same as
uniocular
Binocular visual acuity better than
uniocular
50. Nystagmus blockage syndrome
Inverse relationship with esotropia
Esotropia is a mechanism of blocking the nystagmus
The fixing eye is preferred to be in adduction ,face
turn is in the direction of fixing eye
52. Oculopalatal myoclonus
Type of vertical pendular nystagmus
Coexisting with tremor of the facial
muscles,larynx,palate
Present during sleep
Cause : usually develops months after an infarction or
h’hage involving mollaret triangle
Rx: Gabapentine
53.
54. Ocular bobbing
Characterised by conjugate eye movements,
beginning with a fast downward movement
f/b slow drift back to midline
Causes: 1. comatose patients with massive
pontine lesion
2.metabolic encephalopathy
55. Superior oblique myokymia
Defined as oscillation of one eye due to intermittent
firing of the superior oblique muscle
Produces oscillopsia or intermittent diplopia elicited
by having the patient look in the direction of the
superior oblique muscle
Characterised by monocular,rapid,intorsional
movements
56. Usually benign
No underlying etiology is found
Neuroimaging : r/o post fossa tumors
Refractory cases: surgical weakning of the superior
oblique muscle can be performed
57.
58. Treatment
Nonsurgical : non neurological causes
1.Optical devices
Glasses: overminus lenses stimulate accomodative
convergence and thus dampens nystagmus
Contact lenses: helpful in high refractive errors by
giving good visual stimulus for fusional control
59. Prisms : can be used for 2 purposes
1. to induce fusional convergence by using 7 PD base
out prism in front of each eye
2. pre op evaluation in a patient with face turn
prisms are inserted with the apex in direction of gaze
Useful as a diagnostic trial ,but as a therapeutic
alternative are not helpful
60. Occlusion therapy:
Trials with conventional occlusion have been found to
be effective
As amblyopia gets corrected and vision
improves,nystagmus finally decreases
61. Pharmacologic Mx
These drugs hypothetically inhibit excitatory
neurotransmitters within CNS
Baclofen : congenital nystagmus, seesaw
nystagmus,periodic alternating nystagmus
Carbamazepine: widely used for superior oblique
myokymia
62. Pharmacologic denervation
Botulinum toxin A act by blocking the neuromuscular
transmission
used in 2 distinct ways to dampen nystagmus
3 units of toxin is injected in each of the 4 horizontal
rectus muscles
Single large dose of drug into the retrobulbar space
Effect last for only few months
63. Surgical
Based on 3 principles:
To shift the null position if any to the primary
position
To induce extra convergence innervation by
weakening medial recti,to dampen nystagmus
To reduce the amplitude of the nystagmus by
weakening the muscle force of all recti
64. Kestenbaum surgery
Devised first surgical approach using recession-
resection of all four horizontal recti
Advocated an equal amount of 5 mm for all recti
Left face turn (null in dextroversion):
Right eye: LR recession & MR resection
Left eye : MR recession & LR resection
65. Anderson surgery
Advocated only recessions
Left face turn (null in dextroversion):
Right eye : LR recession
Left eye : MR recession
66. Parks surgery
Recommended lesser amount of recessions and for
medial rectus surgery compared to lateral rectus
surgery.
Advocated a 5,6,7,8 plan
MR recession : 5 mm
MR resection : 6 mm
LR recession : 7 mm
LR resection : 8 mm
67. Carlow TJ : medical treatment of nystagmus and
ocular motor disorders.Int Ophthalmol Clin
1986;28:355
Rosenberg ML,Glaser JS:Superior oblique
myokymia.Ann Neurol 1983;13:667
Helveston EM, Pogrebniak AE : Treatment of acquired
nystagmus with botulinum toxin A. Am J Ophthalmol
1988;106:584