Eye muscles + movements
Muscles |
Nerve Supply |
Action |
Superior Rectus |
III |
Up & out |
Medial Rectus |
III |
Medial |
Inferior Rectus |
III |
Down & Out |
Inferior Oblique |
III |
Up & in |
Superior Oblique |
IV |
Down & In |
Lateral Rectus |
VI |
Lateral |
Sphincter pupillae |
Parasympathetic |
Constricts pupil |
Dilator pupillae |
Sympathetic |
Dilates pupil |
Pathway - Constriction:
Bright Light |
Afferent impulse to optic nerve |
Midbrain @ superior colliculus |
2nd order neuron to Edinger-Westphal nucleus on same & opposite side |
Posterior commisure |
Efferent fibres leave in occulomotor nerve |
Cillary Ganglion |
Constrictor fibres |
Pathological/medical causes of constriction: |
Sympathetic dysfunction, Argyll Robertson, Horner's syndrome |
Pathway - Dilation:
Sympathetic fibres from ipsilateral hypothalamus |
Lateral aspect of BS to spinal cord |
Travels through anterior roots of C8, T1 - Enters sympathetic chain |
Superior Cx ganglion - postganglionic fibres |
Ascends through wall of ICA |
Enters and leaves cranium |
Cillary ganglion to iris |
Joins CNIII, V1 |
Pathological/medical causes of dilation: |
Migraine, OCP, anticholinergenic drugs, antidepressants, NSAIDs, antihistamines, Holmes Adie pupil, parasympathetic dysfunction |
Anisocoria
Unequal pupil sizes (normal size should be 2-6mm) |
Abnormal pupil is the one which does not react to light/darkness |
Larger pupil in bright light/Small pupil in darkness |
Ptosis (eyelid drooping)
Look at: |
Scleral injection (sympathetic dysfunction dilates vessels) |
Angle of medial and lateral canthus (decreased in drooping) |
Larger gap between the folds of the eye |
Obscured Iris |
Is the eyebrow drooping instead? |
How much of eye is drooping? Sympathetic - partial, CN III - Complete |
Argyll Robertson Pupil
Damage to periaqueductal area @ midbrain (neurosyphilis, midbrain lesion, diabetics, alcoholic neuropathies) |
Small, irregular pupils |
unresponsive to light, reactive to accommodation (efferent) |
If accommodation + convergence failed - think parkinsons/tumour of the pineal region |
Holmes-Adie/Tonic Pupil
Degeneration of nerve cells in the ciliary ganglion |
Affects females more |
More likely to be unilateral |
If associated with loss of knee jerks, impairment of sweating = Holmes-Adie Syndrome |
Dilation of pupil causes mistiness/blurred vision/eye pain in bright light |
S&S
Slow/no reaction to direct + consensual light |
Slow pupillary reaction constriction with accommodation |
Slow dilation occurs with relaxed accommodation |
Reacts to pilocarpine (constricts pupil) |
Horner's Syndrome
Interruption of the sympathetic chain |
Causing: Ptosis, miosis, anhydrosis |
Can occur at: |
BS |
Tumour, vascular causes, syringobulbia |
Cx |
Tumour, syringomyelia |
Anterior Roots of C8-T1 |
Tumour, lower plexus palsy |
Middle Fossa |
Tumour, granuloma |
ICA |
Trauma, occulsation, dissection (causes anhydrosis) |
Cx sympathetic chain |
Carcinoma at apex of lung (Pancoast tumour) |
Lesions:
Where |
S&S |
Canverneous sinus |
Horners + CN VI, V, IV abnormality |
Postcx ganglion on right |
Right runk, Right Arm + leg, face and eye |
Pre cx ganglion on right |
Spare right leg, effects right arm, face and eyes |
Descending pathways on right (hypothalamus - spinal cord) |
Trunk and lower limb, arm + face on right side |
Marcus Gunn
AKA - Relative afferent pupil defect (RAPD) |
Swinging light test - pupils dilate when bright light is swung from affected eye to unaffected eye, pupil constriction normal in unaffected eye |
Causes |
Lesion of optic nerve |
| |
Glaucoma |
| |
MS |
| |
Severe retinal disease |
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