Week 2.06 Nystagmus Flashcards
What are the three main mechanisms for maintaining steady gaze
1) Fixation – relies on well developed fovea
2) Vestibulo-ocular reflex – tend to maintain steady gaze when head moving or body moving
3) Gaze holding system
2 types of abnormal fixation:
Nystagmus
Saccadic intrusion/oscillations
Define nystagmus
Rhythmic involuntary oscillation of the eyes
What are the classifications of nystagmus
Physiological - normally in everyday, not clinically significant
Infantile - most common, during infancy
Acquired - due to some abnormality or disease situation
What is physiological broken up into
Optokinetic
Vestibular
End point
Infantile
Manifest - latent
Congenital
Acquired
Gaze - evoked
Downbeat
Inter-nuclear ophthalmoplegia
Vestibular
See-saw
What’s the prevalence of congenital infantile nystagmus
17/100,000
Physiological nystagmus examples
End point nystagmus - extreme ocular motility movement
Post rotational nystagmus - spinning round n round
Induced caloric testing (COWS) - squirt cold or warm water into ear. Cold in opposite direction, warm in same direction
Optokinetic nystagmus - train
Voluntary nystagmus - party trick
Infantile nystagmus
Can be congenital and manifest/latent
Associated with:
Albinism
Optic nerve hyperplasia
Congenital cataract
Idiopathic
Spasmus nutans
- reported by px
- head wobble with nystagmus
- toddlers 2-3yrs
- onset 3-18months
- fine rapid eye movements, jerky, small amplitude, high frequency
- resolve spontaneously by age 3yrs
- benign, can be associated with CNS disease
Ataxic nystagmus
- Occurs in abducting eye in internuclear opthalmoplegia INO
Downbeat nystagmus
Fast downward beat
Upbeat nystagmus
Caused by drug intoxication
Associated with brain lesion
Convergence retraction nystagmus
Jerk nystagmus
Fast phase generating convergence and retraction of globe into orbit
Parinauds syndrome
Vertical gaze palsies
Loss of light reflex
Impaired convergence - convergence retraction nystagmus
See saw nystagmus
Associated with chiasmal lesions
One eye elevates and intorts followed by depression and extrusion of the other eye
May be associated with a chiasmal lesion
What are the different onsets for the different nystagmus types
Congenital - 6 months
Manifest-latent nystagmus - 6-12 months
Acquired - any age
What does pendular oscillation mean
Equal velocity in both directions
