Eye movement disorders Flashcards
List the two gaze centres in the reticular formation
- PPRF (paramedian) next to the abducens nucleus is the horizontal gaze center
- The rostral interstitial nucleus (rostral iMLF) in the midbrain reticular formation near the oculomotor nucleus is the vertical gaze center.
Describe the combined effect of the six extraocular muscles and the neural systems in place to aid this
The eye is moved by the six extraocular muscles to keep the fovea fixed on target.
- Six neuronal control systems keep the eyes on target:
1. Saccadic eye movements shift the fovea rapidly to a new visual target.
2. Smooth-pursuit movements keep the image of a moving target on the fovea.
3. Vergence movements move the eyes in opposite directions so that the image is positioned on both foveae.
4. Vestibulo-ocular reflexes hold images still on the retina during brief head movements.
5. Optokinetic movements hold images stationary during sustained head rotation or translation.
6. The fixation system holds the eye stationary during intent gaze when the head is not moving.
Define the following: primary position, duction, version, vergence, strabismus, tropia, phoria; eso/exo/hyper
- Primary position – (looking straight ahead)
- Duction – rotation of the eye while it alone is viewing
- Version – the movement of both eyes together
-
Strabismus – a misalignment or deviation of the visual axes
- Tropia – relative deviation of visual axes with both eyes viewing (manifest misalignment)
- Phoria – relative deviation of visual axes with one eye covered (latent misalignment)
- Eso-, Exo-, Hyper- - divergent, convergent, vertical misalignment
Duction
The term duction refers to the movement of one eye. All uniocular rotations are termed ductions.
Versions
Synchronous, simultaneous movements of the two eyes in the same direction are called versions. They enlarge the field of view and bring the object of attention onto the fovea. Versions are either voluntary or involuntary and can be horizontal, vertical, and oblique.
Vergences
Synchronous simultaneous movements of the two eyes in opposite directions are called vergences. They are disconjugate movements, i.e., eyes move in opposite directions, producing a convergence or divergence of each eye’s visual field to focus an object that is near or far.
Describe III palsy
-
Oculomotor nerves
- Outer parasympathetic fibers – ciliary muscles & sphincter pupillae
- Inner somatic fibers - Levator Palpebrae superioris, Four Extraocular muscles – SR, IR, MR, IO
III Nerve Palsy Details
- Presentation
- Complete ptosis or incomplete
- Eyes-down & out otherwise known as ocular deviation - LR and SO spared
- Pupil not dilated/dilated depending on if outer fibres are compressed
Describe the presentations and causes of types of III palsy
- complete pupil sparing third nerve palsy
- presents with complete ptosis, eyes down and out, inability to adduct depress or elevate eye, pupil not dilated
- caused by ischaemia of central part of 3, hypertension, diabetes, hypercholesterolaemia, infl
- complete non pupil sparing
- complete ptosis, down and out, inability to adduct depress or elevate; pupil dilated
- caused by compression of peripheral part of 3, most commonly from PCOMM aneurysm
- incomplete pupil sparing
- variable ptosis, variable inability to adduct depress or elevate, pupil not dilated
- caused by ischaemia of various distributions of CN III
Describe 4 palsy
-
Trochlear Nerve
- Innervates the superior oblique muscle
- Intorsion & Depression
IV Nerve Palsy Details
- Presentation
- Vertical & Torsional diplopia more severe in downgaze (Reading, Eating, Walking downstairs)
- Lateral gaze towards the affected side
PARKS-BIELSCHOWSKY 3-step test
- Identify the eye with hypertropia in the primary gaze
- Determine if hypertropia is greater on right or left gaze
- Determine if hypertropia is greater on right or left head tilt
Describe 6 palsy
-
Abducent Nerve –Longest intracranial course
- Nucleus- dorsal pons-courses superiorly & anteriorly and leave at the pontomedullary junction –-subarachnoid space- cavernous sinus- superior orbital fissure- orbit
- Most common oculomotor paralysis in Adults
- Increased intracranial pressure/ Ischemia/Trauma
-
Symptoms
- Horizontal Diplopia
- Worse when looking to the direction of the affected eye
- Also worse when Fixating at a distance than at near
- Compensatory head turn to the affected side
Describe presentations of MG and thyroid ophthalmopathy
Thyroid ophthalmopathy
- Eyelid retraction
- Proptosis
- Extraocular muscle dysfunction
- Conjunctival hyperemia
- Eyelid oedema
Neuromuscular junction Disorder- Myasthenia Gravis
- Neuromuscular disorder causing weakness and fatigue
- Especially notable in eyes as dependent on Ach
- Ocular myasthenia – Eye muscles
- Ptosis/ Diplopia
Describe SOF, orbital apex and cavernous sinus syndromes
Superior orbital fissure syndrome
- Cranial nerves (III, IV, V, and VI) that enter the orbit through the superior orbital fissure (SOF)
- Chemosis
- Complete Ptosis
- Proptosis
- EOM restriction
- Decreased corneal sensation
- Tehrani et al 2017
Orbital Apex syndrome
- Vision loss from optic neuropathy
- Painful Ophthalmoplegia due to the involvement of ocular motor nerves
- Proptosis
- Reduced corneal sensation/facial pain
- Badakere et al 2019
Cavernous sinus syndrome
- A condition characterized by multiple cranial nerve palsies manifesting with ophthalmoplegia, ptosis, and facial sensory loss due to involvement of adjacent cranial nerves
- Kuiper at al. 2017
Describe congenital strabismus
- Misalignment of an eye in relation to the other
- Eye deviation present at birth or develops during the first six months
- Types- concomitant, intermittent, latent
- Concomitant- The angle of deviation of the eye is constant.
- Treat with Glasses/Temporary eye patch/Surgery
Describe nuclear and brainstem pathologies
Nuclear lesions/Brainstem pathologies
- Bilateral deficits
- Superior Rectus- Contralateral CN III subnuclei- paralysis of the contralateral SR
- LPS i.e. levator palpebrae superioris -one subnucleus- central caudal lesions- Bilateral ptosis
- Brainstem
- Weber syndrome- Contralateral Hemiplegia & III nerve palsy
- Benedikt’s syndrome- Rednucleus + III nerve Tremor &3rd nerve
- Nothangel’s syndrome- Ataxia +III nerve palsy
Describe supranuclear lesions and some nuclear lesions
- Gaze palsy – Paresis of conjugate eye movements
- Cortical gaze center- Supranuclear gaze palsy
- Brainstem gaze center- Nuclear gaze palsy
- Horizontal Gaze palsy- Typically unable to move either eyes beyond the midline in one direction. Eyes are deviated constantly to the opposite side.
- Patient should turn his/her head towards the side with gaze palsy
- Contralateral frontal/ ipsilateral pontine lesions
- Horizontal gaze palsy to same side – PPRF+ Abducent nucleus
- Internuclear ophthalmoplegia - MLF
- One and half eye syndrome – MLF+ PPRF + Abducent
- Internuclear ophthalmoplegia - MLF
- One and half eye syndrome – MLF+ PPRF + Abducent
Pontine lesions Vs Supranuclear lesions
- Oculocephalic/ Doll’s eye maneuver
- Passive horizontal rotation of the head directly stimulates the 6th nerve nucleus via the vestibular ocular reflex
List vertical gaze palsy syndromes
- Vertical eye movements are generated in the rostral interstitial nucleus of Cajal.
- Parinauds syndrome
- Progressive supranuclear palsy
Distinguish between saccadic and nystagmus
Nystagmus or Saccadic Oscillations
- Saccadic oscillations are initiated by saccadic eye movements.
- Nystagmus is initiated by smooth eye drifts, and the fast phase in jerk nystagmus is corrective.
Describe nystagmus
- Involuntary biphasic rhythmic ocular oscillation.
- Initiated by a slow eye movement that drives the eye off target, followed by a fast movement that is corrective (jerk nystagmus).
- Another slow eye movement in the opposite direction (pendular nystagmus).
Nystagmus Characteristics
- The direction of nystagmus is conventionally named in the direction of the corrective quick phases that return the eyes toward their target.
- Nystagmus usually arises from lesions in the:
- Vestibulo ocular system (VOR)
- Gaze-holding system
- Smooth pursuit and optokinetic system.
Classification of Nystagmus
- Based on etiology:
- Congenital
- Acquired
- Based on the type:
- Pendular nystagmus
- Jerk nystagmus
- Based on the direction:
- Horizontal
- Vertical
- Based on pathophysiology:
- Physiological
- Pathological
- Based on the synchronicity:
- Conjugate nystagmus
- Dysconjugate nystagmus
Characteristics of Nystagmus: Pendular versus Jerk
- Pendular nystagmus: both phases are slow.
- Jerk nystagmus: If one phase is a saccade (quick phase), which alternates with a slow phase.
- Plane: horizontal, vertical, torsional, or combined form (e.g., rotary, elliptical).
