Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

TK Yr 3 GP Ophthalmology > S8) Binocular vision, Extra-ocular muscles, axes and terminology > Flashcards

S8) Binocular vision, Extra-ocular muscles, axes and terminology Flashcards

1
Q

Why do we have binocular vision? (why do we have two eyes?)

A
  • Allows for wider field of vision and depth perception → enabling 3D vision (stereoscopic vision)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What needs to be ensured for binocular vision?

A
  • visual axis of both eyes need to be aligned
  • eyes need to co-ordinate and move together → called conjugate eye movement
  • This is vital so that 2 images that reach the cortex are ‘fused’ so perceived as one by the brain
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What can misalignment of visual axes cause and why?

A
  • Diplopia
  • Misalignment of two visual axes image focuses on different area of each retina (usually they should hit the same point of the retina in both eyes)
  • .: brain is unable to ‘fuse’ - thus we see 2 seperate images
  • → Diplopia (double-vision)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is diplopia?

A
  • double vision - where 2 images seen
  • can be displaced horizontal, vertically and/ or diagonally depending on misalignment between the 2 eyes.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

If a pt covers over one of his eyes e.g. by closing his eyelid, or covering with a hand, his double vision immediately improves: explain why this happens.

A
  • Sensory only from one eye .: there is no misalignment of the visual axis as 2 eyes are not involved .: nothing to confuse with between the 2 eyes as there is only one sensory input.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

There are two types of muscles of the eye and orbit. They are extrinsic and intrinsic muscles.

What are the extrinsic muscles? What is their innervation?

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

There are two types of muscles of the eye and orbit. They are extrinsic and intrinsic muscles.

What are the intrinsic muscles? What is their innervation?

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Identify the 6 extra-ocular muscles of the eye.

A
  • Superior recti
  • Inferior recti
  • Medial recti
  • Lateral recti
  • Superior oblique
  • Inferior oblique
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the 4 recti muscles?

A
  • Superior
  • Inferior
  • Medial
  • Lateral
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the 2 oblique muscles in the eye?

A
  • Superior oblique
  • Inferior oblique
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Where do the extra -ocular muscles originate?

A

Apex of the orbit, except inferior oblique arises from the floor of the orbital cavity anteriorly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the common tendinous ring?

A

a fibrous cuff that surrounds the optic canal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Which muscles arise from a common tendinous ring?

A

The 4 recti muscles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Where do the extra-ocular muscles insert?

A

sclera of the eye

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the extra-ocular muscles innervated by?

A
  • LR6SO4
  • Lateral rectus → CN VI
  • Superior oblique → CN IV
  • Rest of the muscles by CN III
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Observe this picture. Appreciate it ;)

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

When looking at the eye, we see 2 axis. What are they?

A
  • Visual axis (axis of the eyeball) - in resting gaze, when we look straight ahead, the visual axis of our eyeball is straight ahead
  • Axis of the orbit - relates to the angle in which the extra-ocular muscles insert into the eye
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Why are there several actions of movements on the globe and not just simply up and down for some of the extra-ocular muscles?

A
  • The extra-ocular muscles run in line with axis of orbit
  • Therefore some muscles attach at an oblique angle - those attaching to superior and inferior surfaces of globe
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Identify the labels on the 3D model of the right eye.

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

The primary resting gaze (position at rest) depends on …

A
  • equal and opposite pull of all extra-ocular muscles
  • read picture
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

When we change the position of our gaze, what is occurring muscles wise?

A
  • exert greater pull through action of certain extraocular muscles, while antagonists relax
  • read slide
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How would you..

  • Abduct
  • Adduct
  • Internally rotate
  • Externally rotate
  • Elevate
  • Depress

the eye….

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What muscles are causing these eye movements?

A

Eye adduction → Medial rectus muscle - inserts at the medial aspect of the sclera

Eye abduction → Lateral rectus muscle - inserts at the lateral aspect of the sclera

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What muscle causes eye abduction?

A

Lateral rectus muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What muscle causes eye adduction?

A

Medial rectus muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is the origin and insertion of superior rectus muscle?

A
  • Origin: Apex of the orbit
  • Inserts: obliquely into superior anterolateral surface of globe
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is the action of superior rectus muscle at primary resting gaze?

A
  • Elevate
  • slightly adducts (pulls eye medially)
  • slightly intorts (internally rotates)
28
Q

What is the action of superior rectus muscle when the eye is positioned laterally i.e. abducted?

A
  • More powerful elevator
29
Q

What is the origin and insertion of the Inferior rectus muscle?

A
  • Origin: Apex of the orbit
  • Insertion: antero-inferior surface of globe
30
Q

What is the action of inferior rectus muscle at primary resting gaze?

A
  • Depress
  • slightly adducts (pulls eye medially)
  • Slightly exorts (externally rotates)
31
Q

What is the action of inferior rectus muscle when eye is positioned laterally i.e. abducted?

A
  • More powerful depressor
32
Q

What is the origin and insertion of Superior Oblique muscle?

A
  • Origin: apex of orbit, passes through trochlea
  • Insertion: Superior-posterior aspect of globe
33
Q

What is the action of superior oblique muscle at primary resting gaze?

A
  • Intort (internally rotate)
  • Depress
  • Slightly abducts (pull eye laterally)
34
Q

What is the action of superior oblique muscle when the eye is positioned medially i.e. adducted?

A
  • more powerful depressor
35
Q

What is the origin and insertion of the inferior oblique muscle?

A
  • Origin: Antero-medial surface of floor of orbit
  • Insertion: Infero-posterior aspect of globe
36
Q

What is the action of inferior oblique muscle at primary resting gaze?

A
  • Extort
  • Elevate
  • Slightly abduct (pulls eye laterally)
37
Q

What is the action of inferior oblique muscle when the eye is positioned medially i.e. adducted?

A
  • More powerful elevator
38
Q

Summary image actions of SR, IR, Obliques (starting from primary resting gaze)

A
39
Q

Which extra-ocular muscles have an action in elevating the eyeball?

A
  • Superior rectus muscle
  • Inferior oblique muscle
40
Q

Which extra-ocular muscles have an action in depressing the eyeball?

A
  • Inferior rectus muscle
  • Superior oblique muscle
41
Q

Which extra-ocular muscles are stronger elevators and depressors of the eyeball when the eye is in the adducted position?

A
  • Strong elevator → inferior oblique muscle
  • Strong depressor → superior oblique muscle
42
Q

Which extra-occular muscles are stronger elevators and depressors of the eyeball when the eye is in the abducted position?

A
  • Superior rectus muscle → strongest elevators
  • Inferior rectus muscle → strongest depressors
43
Q

Consistency of activity in all extra-ocular muscles on the eyeball - at resting gaze, there is equal and opposite pull.

If a muscle (s) weakened, what influence will it have?

A

It’s ‘influence’ is lost/ reduced

Other muscle actions no longer antagonised

.: resting position of eyeball may deviate → resulting in strabismus (squint) due to actions of remaining working muscles

There may also be difficulties with moving eye in certain directions of gaze depending on the muscle weakness.

44
Q
A
45
Q
A
46
Q

How would you clinically test for the lateral rectus muscle?

A

Ask patient to follow your finger

Test abduction of the eye

47
Q

How would you clinically test for medial rectus muscle?

A

Ask patient to follow your finger

Test adduction of the eye

48
Q

How do we test for superior rectus muscle?

A
  1. Bring eye laterally first (abducted) - starting position of the eye
  2. Then ask patient to look up and down.
  3. Look up → superior rectus muscle
49
Q

How do we test for inferior rectus muscle?

A
  1. Bring eye laterally first (abducted) - starting position of the eye
  2. Then ask patient to look up and down.
  3. Look down → inferior rectus muscle
50
Q

How do we test for inferior oblique muscle?

A
  1. Bring eye medially first (adducted) - starting position of the eye
  2. Then ask patient to look up and down.
  3. Look up → inferior oblique muscle
51
Q

How do we test for superior oblique muscle?

A
  1. Bring eye medially first (adducted) - starting position of the eye
  2. Then ask patient to look up and down.
  3. Look down → superior oblique muscle
52
Q

Ocular misalignment can result in strabismus. Who is it commonly seen in and why?

A
  • common in children (congenital or develops in infancy)
  • idiopathic
53
Q

What is the cause of strabismus in adults?

A
  • In adults → ‘acquired’ due to pathology or disease involving no. of different structures
  • e.g Neuromuscular junctions e..g Myasthenia gravis
  • Nerves supplying the muscles ( CNIII, IV, VI)
54
Q

Cranial nerve in the eye, can be affected by….

A
55
Q
A
56
Q

CNIII palsies can be due to 2 categories. What are they and what happens to the pupil?

A
  1. Vasculopathic (microvascular) lesions e.g. diabetes/ hypertension - PUPIL SPARED
  2. Compressive lesions (raised ICP, tumour, posterior communicating artery aneurysm) - PUPIL INVOLVED
57
Q

What does the trochlear nerve supply in the eye?

A
  • innervates the superior oblique muscle .: intort, and depress and abduct eye
58
Q

If there is a trochlear nerve palsy, what happens?

A
  • in resting gaze, EXTORTED, slightly elevated and abducted (unopposed actions)
  • extortion of eyeball compensated by head tilt (not seen in image)
59
Q

What might someone say with a trochlear nerve palsy when they look down and medially? Why?

A
  • worsening diplopia esp walking downstairs, reading
  • because SO is main depressor of the eyeball when in adduction → SO is weak .: this action is affected !!!
60
Q

What happens in an abducens nerve palsy?

A
  • lateral rectus muscle weakness .: abduction lost .: unopposed adduction by the medial rectus muscle
61
Q

In an abducens nerve palsy, when would diplopia worsen?

A
  • made worse on horizontal gaze towards eye affected
62
Q

What is the most likely cause of CNIII, IV, and VI lesions?

A

vasculopathic

– pts will be otherwise asymptomatic - apart from signs/ symptoms directly relating to CN lesion

– lesions usually self-resolve within few months

63
Q

History will help give a clearer indication for more concerning underlying cause …such as

A
64
Q

There are two types of muscles of the eye and orbit. They are extrinsic and intrinsic muscles.

What are the extrinsic muscles? What is their innervation?

A
65
Q

Fill this table out.

A
66
Q

SUMMARY OF EXTRA-OCULAR MUSCLES, INNERVATION, CLINICAL TESTING

A

TK Yr 3 GP Ophthalmology (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions