OCULAR MOTILITY Flashcards
Sherrington’s Law
Says that agonist and antagonist EOMs of the same eye are reciprocally innervated.
Hering’s law of equal innervation
Synergistic muscles of the two eyes must receive equal innervation. “Yoke muscles”
VOR
Stabilizes images on the fovea during brief head movement.
Eye movement of equal magnitude to head movement but in opposite direction.
-occurs rapidly with very small latency
-300 deg/sec, latency 15msec
Ocillopsia
Sensation of objects moving up and down in the visual field
-acquired nystagmus often report this
Vertigo
Sensation of the body moving around in the environment
Testing Vestibular dysfunction
- oculocephalic testing
- caloric testing
- rotational testing
Jerk nystagmus
Characterized by slow and fast phase.
Pendular nystagmus
even ack and forth movement of the eyes.
Direction of gaze where the nystagmus has the lowest amplitude is
Null point
Direction where the nystagmus changes direction is
The Neutral point
End point nystagmus
Small intermittent conjugate jerk nystagmus apparent in extreme >30 degree from midline, horizontal position of gaze . Less commonly vertical often worse when patient is tired.
Damage to the right FEF results in impaired saccades toward what direction
To the left ‘ the side opposite the lesion ‘ resulting In the eyes turning to the right “toward the side of the lesion”
Pursuits
Are slow
Latency of 125msec and velocity of 50degree/second
- controlled by the Parietal lobe
-Parietal lobe lesion will cause impaired pursuit toward the ipsilateral side.
Cogwheelong
Abnormal pursuit , step like eye movement
Proximal vergence
Degree is small, usually neglected when measuring vergence movement .
-convergence is associated with a person’s awareness of a near target.
Fusional vergence
Initiated by retinal image disparity.
Decompensated phoria
Large phoria that the patient has previously compensated for, but is now unable to do so as he tries over time, resulting in tropics and symptoms of diplopia.
Comitant deviation
Misalignment in all direction.
Findings indicates a decompensated phoria
Noncomitant
Finding indicates an anatomical muscle restriction or palsy
Duanes’s retraction syndrome
- Structural abnormalities of muscles or innervational issue arising abnormality of CN VI and CN III nuclei.
- All three types are associated with globe retraction and narrowing of the palpebral fissure with addiction.
- violation of Sherrington’s law
Dissociated nystagmus
Amplitude of oscillation differ in each eye.
Disconjugate or disjunctive nystagmus
Direction of the ocillations differ between the 2 eyes.
Eccentric /End gaze nystagmus
Few beats in the extremes of horizontal gaze. More in older patients Not pathological unless -persistent -asymmetric -accompanied by other feature.
OKN
Nasal to temporal OKN is absent in infants until 3-4 months of age.
-slow phase in the direction of rotation of the drum
Infantile or congenital nystagmus
Visual attentions and fixation esp distance will amplify.
On near target, it dampens
Heimann-Bielschowsky phenomenon
Monocular nystagmus with long standing decreased vision.
Caused from optic atrophy or amblyopia .
Persist even when reversible corrected like dense cataract .
Monocular nystagmus
Life threatening
Vertical or elliptical
Spasmus nutans
Vertical nystagmus
Accompanied by head nodding and abnormal head movement .
Neuroimaging should be done
Nystagmus goes away in first decades
Meniere disease
Vestibular dysfunction associated with auditory symptoms, progressive , may be long symptoms free intervals
Causes of
Gaze-evoked nystagmus
Jerk nystagmus at extreme gaze
Alcohol
Sedatives
Anti-convulsants
Posterior fossa disease
