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Opthalmology > The Visual Pathway and Eye Muscles > Flashcards

The Visual Pathway and Eye Muscles Flashcards

1
Q

Two types of ocular muscles

A

Intrinsic muscles

Extrinsic muscles

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2
Q

Function of intrinsic ocular muscles

A

Control pupil diameter

Helps alter lens curvature to enable to see near objects

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3
Q

Function of extrinsic ocular muscles

A

Move the eye

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4
Q

Another name for extrinsic ocular muscles

A

Extraocular muscles

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5
Q

What are the intrinsic eye muscles?

A

Ciliaris
Constrictor pupillae
Dilator pupillae

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6
Q

Where is the Ciliaris found?

A

In the ciliary body

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7
Q

Where is the constrictor pupillae found?

A

In iris at pupillary border

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8
Q

Where is the dilator pupilae found?

A

Radially running muscle in iris

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9
Q

What is the Ciliaris innervated by?

A

IIIn Parasympathetic

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10
Q

What is the constrictor pupillae innervated by?

A

IIIn Parasympathetic

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11
Q

What is the dilator pupillae innervated by?

A

Sympathetic (from plexus around blood vessels)

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12
Q

What are the 6 extrinsic ocular muscles?

A 
Medial rectus 
Lateral rectus
Superior rectus 
Inferior rectus 
Superior oblique 
Inferior oblique
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13
Q

Where do the recti muscles arise from?

A

The apex of the orbit from an annular fibrous ring

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14
Q

Where does the superior oblique muscle arise from?

A

The roof of the orbit posteriorly

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15
Q

Where does the inferior oblique muscle arise from?

A

The floor of the orbit anteriorly

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16
Q

What muscle is found above the superior rectus?

A

Levator palpebrae superioris (LPS)

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17
Q

What does the LPS do?

A

Elevates the upper eyelid

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18
Q

Where do the recti muscles insert onto the sclera?

A

Anteriorly

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19
Q

Where do the oblique muscles insert onto the sclera?

A

Posteriorly

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20
Q

Innervation of the superior oblique

A

Trochlear nerve (IV)

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21
Q

Innervation of the lateral rectus

A

Abducent (VI)

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22
Q

Innervation of all of the eye muscles apart from LR and SO

A

Oculomotor nerve (III)

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23
Q

Where does the SO originate from?

A

Lesser wing of sphenoid

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24
Q

4 main movements of the eye

A

Abduction
Adduction
Intortion
Extorsion

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25
Q

Action of medial rectus

A

Adduction

26
Q

Action of lateral rectus

A

Abduction

27
Q

Action of superior rectus

A
  1. Elevation
  2. Adduction
  3. Intorsion
28
Q

Action of inferior rectus

A
  1. Depression
  2. Adduction
  3. Extorsion
29
Q

Action of superior oblique

A
  1. Intorsion
  2. Depression
  3. Abduction
30
Q

Action of inferior oblique

A
  1. Extorsion
  2. Elevation
  3. Abduction
31
Q

Neumonic to remember some movements of eye muscles

A

RADSIN

  • recti ADductors
  • Superior INtortors
32
Q

Two types of squint

A

Esotropia

Exotropia

33
Q

What is esotropia?

A

Manifest convergent squint

34
Q

What is exotropia?

A

Manifest divergent squint

35
Q

What is another name for squint?

A

Strabismus

36
Q

Functional consequences of squint

A

Amblyopia

Diplopia

37
Q

What is amblyopia?

A

Lazy eye

38
Q

What is diplopia?

A

Double vision

39
Q

Pathology of amblyopia

A

When brain suppresses the image of one eye leading to poor vision in that eye without any pathology

40
Q

What is your visual field?

A

Everything you see with one eye (including in the periphery)

41
Q

How do you test the visual field?

A 
Confrontation test (outpatient screening)
Automated periphery
42
Q

How do you test visual acuity?

A

Reading a chart

43
Q

How are images from your visual field formed?

A

Formed upside down and inverted into your retina

44
Q

Describe the visual pathway

A

All fibres from the eye pass through the optic nerve to the optic chiasma
At the optic chiasma the medial (nasal) fibres cross to the opposite side than the temporal fibres
Fibres from the optic tract synapse at the LGB of the thalamus
From here the optic radiation passes behind the internal capsule (retro-lentiform fibres) to reach the primary visual cortex

45
Q

What does the optic tract consist of?

A

Fibres from the lateral (temporal) half of the ipsilateral eye and the crossed over nasal fibres from the contralateral eye

46
Q

Where do the fibres from the optic tract synapse?

A

Lateral Geniculate body (LGB) of the thalamus

47
Q

Where is the primary visual cortex found in the brain?

A

Occipital lobe

Area 17

48
Q

What damage would be seen if the right optic nerve was damaged?

A

Blindness in one eye

49
Q

What damage would be seen if the optic chiasma was disrupted in the middle?

A

Bitemporal hemianopia

50
Q

What damage would be seen if the right optic tract was damaged?

A

Contralateral homonymous hemianopia

51
Q

What damage would be seen if the optic radiation is damaged?

A

Contralateral homonymous hemianopia

52
Q

What happens to the pupillary reaction when there is increased illumination?

A

Parasympathetic

Both pupils constrict

53
Q

What happens to the pupillary reaction when there is decreased illumination?

A

Sympathetic

Pupils dilate

54
Q

Where do fibres destined to activate the pupillary reflex go?

A

NOT THE LGB
They leave optic tract to go to the midbrain (where the IIIn nucleus is situated)
Part of IIIn nucleus is the EWN for parasympathetic fibres.
THE PUPILLARY REFLEX GOES TO THE EWN OF BOTH SIDES

55
Q

What does EWN stand for?

A

Edinger-Westphal nucleus

56
Q

Efferent limb of the pupillary reflex

A

From EWN to
Preganglionic parasympathetic fibres pass through IIIn into orbit to
Parasympathetic fibres go to and synapse in ciliary ganglion
Postganglionic fibres go through short ciliary nerves to the constrictor pupillae
Pupillary constriction of both sides

57
Q

What is the name of pupils having different sizes?

A

Anisocoria

58
Q

Common causes of absent/abnormal pupillary reflex

A

Any abnormality of the afferent limb/centre/efferent limb of the reflex
Disease of the retina - detachment/degenerations or dystrophies
Diseases of the optic nerve - e.g. optic neuritis (frequently seen in MS)
Diseases of III CN (efferent limb)

59
Q

What is horners syndrome?

A

Anisocoria due to damage to the sympathetic innervation to the pupil

60
Q

Symptoms of horners syndrome

A

Anisocoria
Ptosis on affected side
Anhidrosis on affected side
Miosis on affected side

61
Q

What is ptosis?

A

Drooping of eyelid

62
Q

What is anhidrosis?

A

Loss of sweating on the effected side

Opthalmology (8 decks)

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