Week 6 - The Orbit, Extraocular Muscles and The Eye Flashcards

1
Q

Outline the direct and consensual light reflexes. (direct is the left, in this case)

A
  1. Light in left pupil
  2. Sensory afferent in left retina - CN II
  3. To brainstem - pretectal nucleus
  4. Connection with EDW nuclei - left and right
  5. Parasympathetic fibres from EDW leave brainstem
  6. Hitch-hike on CN III - left and right
  7. Pass via ciliary ganglion
  8. Reach sphincter pupillae
  9. Direct - left, consensual - right
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2
Q

Why is the cornea not affected in conjunctivitis?

A

Because the conjunctivae ends at the limbus, hence the cornea is not affected because the conjunctivae does not overlie the cornea

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3
Q

What is a Meibomian cyst (chalazion) due to?

A

A blocked tarsal (meibomian gland) which lie posterior to the eyelash, within the tarsal plates (eyelids)

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4
Q

What is a stye (external hordeolum) due to?

A

Infection of a sebaceous gland situated at the base of the eyelash (lash follicle)

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5
Q

Why can’t the eye be elevated in an orbital blow-out fracture?

A

Due to trapping of the inferior rectus muscle, which prevents the eye being elevated by the other extra-ocular muscles

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6
Q

Why is there reduced sensation over the cheek in an orbital blow-out fracture?

A

Due to damage of the inferior (or infra-orbital) branch of the trigeminal nerve, maxillary branch V2 which emerges just below the orbit through the infra-orbital foramen

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7
Q

Why might suturing a wound caused by an orbital blow-out fracture not be so straightforward?

A
  • Injury to the area of the face near the medial angle of the eye may involve injury to the lacrimal canaliculi and nasolacrimal duct
  • If such a wound is repaired without consideration to the lacrimal drainage system immediately beneath, the injured ducts can become stenosed as they heal
  • The patient could be left with long-term problems due to excessive tearing and recurrent conjunctivitis due to impedance of tear drainage from that eye
  • Wounds involving this area should be referred to a specialist, and treatment may involving microsurgery and placing a stent through the canaliculi/duct to ensure it remains patent as the wound heals
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8
Q

Superior rectus:

  1. Cranial nerve supply
  2. Clinical movement tested
A
  1. III

2. Move eye up and out

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9
Q

Inferior rectus:

  1. Cranial nerve supply
  2. Clinical movement tested
A
  1. III

2. Moves eye down and out

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10
Q

Superior oblique:

  1. Cranial nerve supply
  2. Clinical movement tested
A
  1. IV

2. Moves eye down and in

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11
Q

Inferior oblique:

  1. Cranial nerve supply
  2. Clinical movement tested
A
  1. III

2. Moves eye up and in

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