Lecture 6 Nystagmus Flashcards
What is nystagmus?
-rhymic, repetitive, involuntary movements of one or both eyes
-can be horizontal, vertical, torsional or a combination
-most common cause of VI in school-aged children
What are the different classifications for nystagmus?
physiological- part of vestibular ocular reflex
(optokinetic, vestibular, endpoint, voluntary)
pathological- damage to the vestibular system
infantile/congenital- secondary to visual defect (retinal dystrophy, albinism) or neurological defect (intra-cranial lesions, drug toxicity, stroke, MS)
types: sensory deficit nystagmus, congenital idiopathic nystagmus (CIN)
acquired: upbeat, downbeat, abducting, monocular, see-saw, convergence retraction
What type of waveforms can you get?
JERK (vestibular)
*Slow phase (pathological) and fast phase (refixation)
*Described by direction of saccade: right beat, upbeat, downbeat
PENDULAR (optokinetic)
*Can occur in any direction
*No fast phase
*Smooth oscillations
*Waveforms may be a combination of jerk/pendular
*May vary with gaze direction
How do you document nystagmus?
*Amplitude: the excursion of the nystagmus
*Frequency: number of oscillations per minute (coarse, medium, or fine)
*Intensity: amplitude x frequency
What is the difference between manifest and latent nystagmus?
*Manifest nystagmus: when both eyes are open. May increase when one eye is covered.
*Latent nystagmus: when one eye is covered. Steady fixation with both eyes open. (Result of an early insult to BV e.g., unilateral cataract, early onset strab)
When does congenital nystagmus develop?
What are the 2 primary forms?
2-6 months
SDN-sensory deficit nystagmus
CIN-congenital idiopathic nystagmus
What is the etiology of CIN?
What is the etiology of SDN?
unknown, may be x linked, autosomal or sporadic.
*Early macular deprivation e.g., dense bilateral cataract, retinal cone dysfunction, albinism (oculo-cutaneous or purely ocular)
*Fundus and media examination, and electro diagnostic testing needed
What is Manifest latent nystagmus?
What is it associated with?
when is it usually detected?
when is it more pronounced?
separate diagnosis to congenital nystagmus. always present. worsens when one eye is covered.
early onset strab, DVD
2 years
when one eye is abducted and in abducted position of gaze.
What is the waveform like in congenital nystagmus?
*Waveform may change during infancy and may initially be present as large roving eye movements.
-Can develop into pendular/jerk.
*Waveform may vary with position of gaze.
What does uniplanar mean?
What direction is congenital nystagmus usually?
horizontal in all directions of gaze (including up and downgaze)
invariable horizontal but may have a rotary component.
What is a null zone?
*Position of gaze of the least movement (nystagmus is the most stable so vision is best)
*Called dampening of nystagmus
*May adopt AHP for best VA
How should you test vision in people with nystagmus?
What is vision like in children with CIN?
What is vision like in children with SDN?
distance and near
with and without AHP
significant AHP=indicator for active management -REFER
better in CIN can be 6/9
worse in SDN 6/60 or less
What symptom is seen in children with congenital nystagmus?
head nodding
compensatory mechanism to improve vision by reducing frequency and asymmetry of nystagmus
If px null zone is to the right, which direction will px have a AHP in?
left
What is spasmus nutans?
what age does it present?
what is it associated with?
*Cause rapid, uncontrolled eye movements head bobbing and holding the neck in an abnormal position.
* Self-limiting.
-presents at 1-2 months
* Disorder disappears by age of 3-4.
*Some cases associated with chiasmal or super-chiasmal lesions in brain. Need neuroimaging on these babies.
What is oscilliopsia?
px with this are likely to have what?
*Not a presenting sign in congenital nystagmus but may be recognised when tired as nystagmus increases in the dark
*Complaints of oscillopsia are suggestive of acquired or voluntary nystagmus
What are the examples of acquired nystagmus and what causes them?
*Upbeat: brainstem lesions
*Downbeat: cerebellar lesions
*Abducting nystagmus-INO (inter nuclear ophthalmalgia) (lesion in medial longitudinal fasciculus). Will have limited adduction of contralateral eye
*Monocular nystagmus: spasmus nutans, tumours of optic chiasm or 3rd ventricle
*See-saw nystagmus: alternating elevation/intorsion of one eye and depression/extrusion of the other: chiasmal/parasellar mass lesions
Convergence retraction nystagmus syndrome: parinaud’s/dorsal midbrain syndrome
What is the treatment of acquired nystagmus?
Removal of the cause
Drugs
Surgery to shift null zone-variable success
Retrobulbar botulinum toxin-limited success, useful in non-ambulant patients (not able to walk)
What is the general management of nystagmus?
*There is no cure for nystagmus
*Need onward referral to ophthalmologist to aid diagnosis.
*Can consult a geneticist
*Correct refractive error to give best VA
What is the management of congenital nystagmus?
*Refraction and correction of all refractive errors (cycloplegic refraction)
*Accurate assessment of near and distance VA
*Near VA should be recorded at 1/3m and their preferred distance
*Ophthalmologist may arrange paediatric assessment and genetic counselling
*They will assess consistence and significance of AHP
*They need to be monitored through childhood
What are the treatment options for nystagmus?
refractive correction: glasses for best VA, contact lenses move with eye os better VA
LVA: magnifers, tinted glasses for glare
PRISMS: not successful if null zone is in extreme positions of gaze.
-give BI prism if nystagmus reduces on convergence
-pirsm should be same strength in both eyes
-Fresnel prism on glasses (moves images into null zone without AHP)
BT: helpful in people with acquired nystagmus associated with MS. can reduce symptoms of oscilliopsia. effects are temporary
WHat drugs can be used in nystagmus treatment?
*Includes alcohol and cannabis
*Gabapentin and Memantine most commonly used
What treatments are there to reduce AHP?
*Surgery to EOMs to move null zone into primary position.
*Surgery has little value if AHP is less than 15 degrees. Wait until child is 8 years old (visually mature).
*Prisms to move visual environment to null point.
*Prisms to reduce nystagmus through forced convergence.
When is surgery offered?
What are the surgical options for nystagmus?
*Offered where there is a marked head turn due to a null point
*Involves detachment and reattachment of the eye muscles
*Results in more natural head position and clear vision
*Can need follow up surgery for corrections
*Some people perceive slowing of eye movements as a result of surgery
*Most px wont meet driving standard
*ROTATE EYES IN DIRECTION OF HEAD TURN (only 5mm resections, won’t work for typical case)
