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Flashcards

Eyes: orbit, reflexes and movements

Caitlin Murphy Medicine English 45 cards

Eyes: orbit, reflexes and movements

Cards in this deck (45)

  1. 1Accommodationenables us to look at and focus upon objects close to the eye
  2. 2Cillary body contraction ...relaxes suspensory ligaments enabling the lens to recoil (makes it fatter)
  3. 3Process of accommodationProcess of accommodation
  4. 4Argyll-Robertson (Prostitute's) pupilNo pupillary reflex but accommodation reflex is ok
    seen in: tertiary neuro syphilis & diabetic neuropathy
  5. 5Edinger-Westphal nuclear damageNo direct or consensual reflex on damaged side
    Pupil dilated & unreactive
    Cause: vascular/tumour/brainstem
  6. 6CN III compressionNo direct or consensual reflex on damaged side
    Pupil dilated and unreactive
    CNIII Compression = loss of all CNIII functions
  7. 7CNIII Vascular lesion= sparing of pupillary functions
  8. 8Superior tarsal muscleSmooth muscle, innervated by sympathetic NS – open eyes more during fight or flight or by pharmacological reasons.
    Not able to open eye by itself.
    Loss will show partial ptosis in the eye
  9. 9All extraocular muscles are innervated by...CN III except:
    Superior oblique (the muscle with a trochlea) = trochlea nerve (CN IV)
    Lateral rectus (the abductor muscle) = abducens nerve (CNVI)
  10. 10—SR – Superior rectus
    IR – Inferior rectus
    MR – Medial rectus
    LR – Lateral rectus
    SO – Superior oblique
    IO – Inferior oblique    SR – Superior rectus IR – Inferior rectus MR – Medial rectus LR – Lateral rectus SO – Superior oblique IO – Inferior obliqueSR – Superior rectus IR – Inferior rectus MR – Medial rectus LR – Lateral rectus SO – Superior oblique IO – Inferior oblique
  11. 11Origin of rectus musclesa common tendinous ring at posterior of point
  12. 12Nerves that come through superior orbital fissureCN III
    CN IV
    CN Va
    CN VI
  13. 13tumour of meningies effect of eyesloss of eye movements
    headache (CNVa)
  14. 14Origin or inferior obliqueantero-medial floor of the orbit
    (is like a hammock sitting under the eye)
  15. 15The 3 perpendicular axis eye can moveBlack axis: Transverse = Look left or right
    Red axis: Sagittal = Look up or down
    Blue axis: Coronal = Torsion (twisting in and out)
    Some muscles bring about combined eye movements    The 3 perpendicular axis eye can move
  16. 16Eye testing pattern and what they testEye testing pattern and what they test
  17. 17Contraction of Lateral rectusabducts eye
  18. 18contraction of medial rectusadducts eye
  19. 19Contraction of the superior rectuselevates the eye
    look up
  20. 20Contraction of the inferior rectusdepresses the eye
    look down
  21. 21Contraction of superior obliquetilts eye downwards
  22. 22contraction of inferior obliquetilts eye upwards
  23. 23Hering's lawextraocular muscles normally have equal and simultaneous innervation
  24. 24If a given CN VI or its nucleus is damagedNo lateral movement of the affected eye.
    Ipsilateral eye rests in adducted position = convergent squint.
    Horizontal diplopia.
    Diplopia worse when looking toward the affected side.
  25. 25CN III is the motor supply for...the x4 muscles that move the eye,
    x1 that opens the eyelid,
    the sphincter pupillae,
    the ciliary body
  26. 26CN III lesion can produceComplete ptosis on affected side.
    Down and out position of affected eye.
    Divergent squint.
    Horizontal and vertical diplopia.
    Dilated pupil on affected side that’s unreactive to direct or consensual light.
    Consensual pupil reflex intact in contralateral (unaffected) eye.
  27. 27Patient can complain of sore neckloss of muscles (due to CN IV lesion) that mean eye can't rotate properly so at rest eye is not pointing straight ahead. Patient bends neck to correct this - hence pain
  28. 28Motor supply to superior obliqueCN IV
  29. 29CN IV lesion can produce:Upward deviation and extorsion (outward rotation) of the affected eye.
    Vertical diplopia: worse when descending stairs / reading paper.
    Torsional diplopia: double vision where the images twisted apart from each other.
    Patient tilts head away from lesion to help prevent diplopia (counteracts extorsion produced by inferior oblique).
  30. 30Track target definitionsmooth pursuit when target is moving
  31. 31stabilise target definitionyou are moving target is not
  32. 32scan target to targetsaccade (fast movement)
  33. 33centre that control eye movementVestibular nuclei & parapontine reticular formation
    Frontal eye field (frontal cortex)
    Saccade centres (several locations)
    Visual association areas
  34. 34what is the medial longitudinal fasciculus?is a neuronal tract that enables conjugate gaze & tracking neck movement
    connects CNIII, IV and VI with vestibular nuclei, cerebellum & neck muscle lower motor neurons
    (makes you look left or right)
  35. 35Pathway of the medial longitudinal fasciculusAction potential travels from CNVI to CNIII
    Involved in lateral gaze (& other things too)
    Under automatic & voluntary control
  36. 36Lesions of the medial longitudinal fasciculus results inInternuclear opthalmoplegia
    Lesion cuts interneuron connections between CN VI & CN IIII
    means you can't move your eyes properly
    Can be bilateral or unilateral
    Can still accommodate
  37. 37vestibulo-occular reflexA rotation of the head is detected, which triggers an inhibitory signal to the extraocular muscles on one side and an excitatory signal to the muscles on the other side (semicircular canal is activated). The result is a compensatory movement of the eyes.
  38. 38Testing of vestibulo-ocular reflex:in comatose patients to determine brain stem function - Doll's eye sign positive is good
  39. 39Signalling to a given lateral semicircular canal increases if......head is rotated to toward & decreases if head is rotated away from it
  40. 40Effect of brainstem stroke on vestibular systemon affected side the lateral semicircular canal is not activated and the patient's eyes drift off to opposite side and snap back (nystagmous)
  41. 41Which direction will a right lateral semicircular canal or vestibular nucleus make the eyes look?to the left
  42. 42Right (VN, LSCC OR FEF) makes you look...Left
    damage causes the eyes to drift/look right
  43. 43Jerk nystagmous definitionRepetitive eye movement with a fast and slow phase
    is described according to the fast phase
    EXAMPLE:
    Slow Phase: Eyes slowly drift left....they look towards the damaged left side
    Fast Phase: Eyes move quickly rightwards back to the midline via action of saccade centres in brainstem & cortex
  44. 44Result of putting cool/cold water into an external auditory meatusit mimics a vestibular system/nucleus lesion on that side
  45. 45Result of cold caloric testcan be used to induce nystagmous & test brainstem function

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Eyes: orbit, reflexes and movements
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Caitlin Murphy
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