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- 1. -QURESHI HAMZA THIRD YEAR
- 2. INTRODUCTION Nystagmus is not a disease, it is manifestation
of diseases involving either the eyes or extra ocular neural
structures with predominant ocular signs. It is a clinical
neuro-ophthalmic puzzle with about forty classifications, none of
which is very accurate. Nystagmus is a disturbance of ocular
posture. Nystagmus is defined as repetitive, rhythmic oscillation
of one or both eyes in any or all fields of gaze. Exact mode of
development of nystagmus is not well understood. During steady
fixation the eyes are motionless, without any to and fro movement,
that is brought about by afferent path, efferent path and intra
cerebral components. Defect in any of them results in involuntary
movements of the eyes, i.e. nystagmus. Ninety percent of nystagmus
are brought about by afferent defect. Rests are efferent in nature.
The afferent nystagmus are due to defective vision. Defective
vision in early infancy is more likely to cause nystagmus. The
common conditions associated with nystagmus areCongenital cataract,
albinism, aniridia, hypoplasia of optic nerve, achromatopsia, and
optic atrophy. The efferent nystagmus are due to ocular motor
disturbance
- 3. Classification Nystagmus can be congenital or acquired.
Congenital nystagmus is always pathological. Nystagmus is described
clinically under following heads: 1. Morphology 2. Plane 3.
Amplitude 4. Frequency 5. Degree
- 4. 1. Morphology i). Pendular nystagmusIt has oscillation of
equal speed and amplitude on each direction like a pendulum of a
wall clock generally in primary position. They can be horizontal,
vertical or rotatory. The horizontal pendular nystagmus is the
commonest type of all nystagmus. The most probable etiology is
sensory deprivation caused due to diminished central vision mostly
of congenital nature. Some of the them may be acquired in children.
Common congenital causes are macular hypoplasia,
achromatopsia,Lebers congenital amaurosis, hypoplasia of optic
nerve, albinism and congenital cataract, albinism, aniridia The
conditions that are acquired in childhood and infancy causing
nystagmus are Developmental cataract, corneal opacities, high
errors of refraction. Sometimes pendular nystagmus may be seen in
many members of the same family. This is called hereditary pendular
nystagmus. Such members do not have any associated ocular or
neurological defects and these cases last for rest of life without
progress. Other causes of pendular nystagmus are: Drug toxicity,
lesions of brain stem, miners nystagmus and acquired unilateral
nystagmus. The horizontal pendular nystagmus has a slow, smooth to
and fro movement equal on both directions. The movements become
milder on convergence. They persist on dim light but disappear on
closure of eyes. The central vision is invariably poor.
- 5. Miners nystagmus This is seen exclusively in coal miners who
have to spend hours in dim light underground and keep a constant
crouched posture with up gaze. They generally have mental fatigue.
The nystagmus is mostly pendular, rarely it may be jerky. It is
present in up gaze. Most of the cases have horizontal nystagmus,
next in frequency are vertical and rarely it may be circular or
oblique. ii). Jerk nystagmus This is a biphasic nystagmus, i.e. it
has a slow phase in one direction and a rapid phase in the opposite
direction. The jerk nystagmus is named after the direction of the
rapid phase, it could be right, left, up or down according to
direction of the rapid phase. The slow phase is the fundamental
phase while the rapid phase is the compensatory phase. The former
is also pursuit phase, the latter is saccadic phase. The causes of
jerk nystagmus can be congenital or acquired. They can be
physiological as well as pathological. The common examples of jerk
nystagmus are: Optokinetic nystagmus, end point nystagmus,
vestibular nystagmus, latent nystagmus, gaze paretic nystagmus,
congenital jerk nystagmus.
- 6. iii. Mixed nystagmus This is rare than the pendular or jerk
nystagmus where the pendular nystagmus is seen in primary position
and jerk nystagmus is seen when the eyes deviate. Null point and
null zone The excursion of the eyes is not equal throughout their
movements. In between the two ends of movement, there is an area
where the nystagmus is least or absent. This distance may be
reduced to a point. The distance is called null zone. The patient
becomes aware of its presence and tries to keep this zone nearer to
the primary position of the eye. If the null point falls outside
the primary gaze the patient develops an abnormal head posture to
maintain the gaze in a position that has least oscillation. Neutral
zone is where the direction of nystagmus changes from one side to
the other.
- 7. 2. Plane of nystagmus can be horizontal, vertical, torsional
or oblique. The horizontal plane is the commonest plane. 3.
Amplitude This is measurement of excursion of the eyeball in
degrees during oscillation. It is graded as fine, medium or coarse.
Fine is less than 5, while coarse (large) is more than 15. The
medium amplitude comes in between. 4. Frequency (rate) This is in
cycles per second and designated as rapid and slow. Generally the
rate varies with amplitude faster the rate, finer the amplitude and
vice-versa. 5. Degrees of nystagmus These are based on Alexanders
law which states that the amplitude of jerk nystagmus is largest in
the gaze of direction of fast component. One the basis of this the
nystagmus has been put in three degrees: i. First degree The
nystagmus is present only in the gaze in the direction of fast
component. ii. Second degrees Nystagmus is also present in position
of primary gaze. iii. Third degree The nystagmus is present in
direction of slow components.
- 8. Classification of nystagmus Nystagmus is a disorders that
has been subjected most probably to maximum number of
classifications, none of which seem to be self-sufficient
encompassing all. The most widely used classification is to
differentiate between two groups: 1. Physiological nystagmus 2.
Pathological nystagmus The next common division is: Congenital
(infantile) Acquired Both the above, can either be due to ocular
causes or nonocular causes. The ocular causes of nystagmus are
Macular hypoplasia, optic nerve hypoplasia, achromatopsia,
albinism, high errors of refraction, congenital cataract, Lebers
congenital amaurosis see above. The ocular nystagmus are congenital
or infantile in nature. They follow the rule of 2-4-6, which is as
follows: i. If the child has poor vision before 2 years of age he
will always develop some type of nystagmus. ii. Between 2 to 4
years, only some children with central loss of vision will develop
nystagmus. iii. If the loss of central vision develops after 6
years of age, chances of developing nystagmus are nil.
- 9. Classification Nystagmus can be either: Jerk - fast one
direction, slow the other Pendular - equal velocity in both
directions Mixed - of above And can be Horizontal/Vertical/Oblique
or Rotary In overwhelming majority of cases both eyes move in a co-
ordinated manner
- 10. Physiological Nystagmus not due to a disease process Has no
benefit, except as a diagnostic tool Not associated with reduced VA
Examples include End point nystagmus Postrotational nystagmus
Induced caloric testing Optokinetic nystagmus Voluntary
nystagmus
- 11. Sensory deprivation Due to a defect in the neural control
of fixation Poor macular function that cannot be restored and
therefore of little clinical significance Typically pendular and
horizontal Reduced by convergence and head posture If a child loses
vision before 2 yrs they will invariably develop nystagmus After 6
yrs they usually do not develop nystagmus In between 2-6years it is
Less predictable
- 12. Motor Imbalance Congential Spasmus Nutans Latent nystagmus
Ataxic nystagmus Downbeat nystagmus Upbeat nystagmus Convergence
retraction nystagmus See-Saw nystagmus Periodic alternating
nystagmus
- 13. CONGENITAL NYSTAGMUS due to a congenital anomaly of the
motor system or to a congenital disorder of vision Inherited as
X-link recessive or autosomal dominant trait may appear during
early childhood but is rarely present at birth. Generally
horizontal jerk type Absent in sleep Visual impairment is
variable
- 14. Spasmus Nutans Nystagmus, involuntary head movements, AHP
Onset 3-18 months of age Fine rapid eye movements; jerky, small
amplitude, high frequency Horizontal, vertical or rotary, or a
combination of these Considerable variation in nystagmus in
different positions of gaze Involuntary head movements comprising
nodding or shaking, or a combination of both; variable. Head
movements do not appear to compensate for eye movement as they are
of a different frequency Most cases resolve spontaneously by age 3
years. Benign, but can be associated with CNS disease, therefore
should be investigated.
- 15. Latent Nystagmus Horizontal jerk nystagmus presents when
the light stimulus is reduced to either eye (eg by occluding). In
latent, no observable movement is present on uncovering and full
BSV is restored. Jerk nystagmus with fast phase towards the
uncovered eye Often noted in early childhood but can be observed in
adults (especially if they have had strabismus surgery or in
DVD)
- 16. Downbeat Nystagmus Has a fast downward beat Pathognomic of
a brain lesion at the cervicomedullary junction at the foramen
magnum
- 17. Upbeat Nystagmus Commonly caused by drug intoxication (eg
phenytoin - used as an anticonvulsant) May be associated with a
brain lesion at the posterior fossa Often worsens in upgaze base up
prisms in reading glasses can be used to force the eyes
downward
- 18. Convergence Retraction Nystagmus Jerk nystagmus Fast phase
generating convergence and retraction of globe into orbit Usually
associated with brain lesion in the pretectal area
- 19. See-Saw nystagmus Usually an acquired motility disorder
associated with chiasmal lesions where one eye elevates and intorts
followed by depression and extorsion of the other eye May be
associated with a chiasmal lesion (bitemporal hemianopia could be
present) Rare
- 20. Periodic Alternating nystagmus Very rare jerk nystagmus
Nystagmus changes amplitude and direction Associated with vascular
or demylinating brainstem disease
- 21. Recording on paper. Up gazeUp right gaze Up left gaze Down
and left gazeDown gazeDown & right gaze
- 22. Interpretation Amplitude : Length of the arrow Frequency :
Number of arrow Direction: Head of arrow Waveform: shape of shaft
of arrow No nystagmus ( null zone )
- 23. Management of nystagmus Lack of precise knowledge about
nystagmus makes its management difficult. The management may be
broadly divided into two parts: 1. Directed towards the systemic
causes that results in nystagmus, i.e. infection, inflammation,
trauma, neoplasm etc. These are outside the domain of
ophthalmologist. They are best treated by neuro physician or neuro
surgeon. 2. Directed towards the ocular manifests. Which is managed
by ophthalmologist and optometrist. The aim of which are: i.
Improve vision ii. Correct physical appearance by way of: a.
Minimize nystagmus b. Correct head posture c. Manage squint and
amblyopia.
- 24. The above goals are achieved by a combination of: a.
Medical treatment b. Optical correction c. surgery: a. The medical
management consists of: i. GABA agonist, anti convulsants,
sedatives and tranquillisers. They are Gaba pentin, baclofen,
clonazepam, valproate, carbamazipine. ii. Retro bulbar injection or
infiltration of spastic extraocular muscle with botulin toxin type
A (Botox). The therapeutic agents are best administered under
supervision of physician. b. Optical correction consists of
salvaging the best correctable vision by: i. Spectacles ii. Contact
lenses iii. Uniocular telescope for distance c. Squint is managed
by: i. Optical correction ii. Prisms they are used to dampen the
action of stronger muscles and place the eyes in position of least
nystagmus. iii. Surgery to correct squint and to move the eyes into
null zone. This is claimed to correct abnormal head posture. The
commonest procedure is known as Kestenbaum Anderson procedure.(is
designed to help realign the head or eliminate face turn in
nystagmus with null point)
- 25. Treatment Aim : to improve VA by Stabilizing the eyes.
Decreasing oscilopsia Shifting neutral zone in any compensatory
head posture
- 26. Treatment Low-vision aids can often help improve vision.
They may include large print or high contrast materials, good
lighting, and magnifying devices. Prevention- There is no known way
to prevent nystagmus.
- 27. Genetic counseling - Autosomal Dominant-A gene for
autosomal dominant congenital nystagmus localizes to 6p12 -
Autosomal Recessive - X-Linked-Mutations in the FRMD7 gene cause
X-linked infantile nystagmus - Genetic counseling can help the
patient and family understand the odds of passing the condition to
their children. Not all cases of early onset nystagmus are
hereditary. - Neurologic or neuro-ophthalmic consultation should be
considered.
- 28. THANK YOU