The Visual Pathway and Eye Muscles

Question 1

Two types of ocular muscles

Answer 1

Intrinsic muscles

Extrinsic muscles

Question 2

Function of intrinsic ocular muscles

Answer 2

Control pupil diameter

Helps alter lens curvature to enable to see near objects

Question 3

Function of extrinsic ocular muscles

Answer 3

Move the eye

Question 4

Another name for extrinsic ocular muscles

Answer 4

Extraocular muscles

Question 5

What are the intrinsic eye muscles?

Answer 5

Ciliaris
Constrictor pupillae
Dilator pupillae

Question 6

Where is the Ciliaris found?

Answer 6

In the ciliary body

Question 7

Where is the constrictor pupillae found?

Answer 7

In iris at pupillary border

Question 8

Where is the dilator pupilae found?

Answer 8

Radially running muscle in iris

Question 9

What is the Ciliaris innervated by?

Answer 9

IIIn Parasympathetic

Question 10

What is the constrictor pupillae innervated by?

Answer 10

IIIn Parasympathetic

Question 11

What is the dilator pupillae innervated by?

Answer 11

Sympathetic (from plexus around blood vessels)

Question 12

What are the 6 extrinsic ocular muscles?

Answer 12

Medial rectus 
Lateral rectus
Superior rectus 
Inferior rectus 
Superior oblique 
Inferior oblique

Question 13

Where do the recti muscles arise from?

Answer 13

The apex of the orbit from an annular fibrous ring

Question 14

Where does the superior oblique muscle arise from?

Answer 14

The roof of the orbit posteriorly

Question 15

Where does the inferior oblique muscle arise from?

Answer 15

The floor of the orbit anteriorly

Question 16

What muscle is found above the superior rectus?

Answer 16

Levator palpebrae superioris (LPS)

Question 17

What does the LPS do?

Answer 17

Elevates the upper eyelid

Question 18

Where do the recti muscles insert onto the sclera?

Answer 18

Anteriorly

Question 19

Where do the oblique muscles insert onto the sclera?

Answer 19

Posteriorly

Question 20

Innervation of the superior oblique

Answer 20

Trochlear nerve (IV)

Question 21

Innervation of the lateral rectus

Answer 21

Abducent (VI)

Question 22

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

Answer 22

Oculomotor nerve (III)

Question 23

Where does the SO originate from?

Answer 23

Lesser wing of sphenoid

Question 24

4 main movements of the eye

Answer 24

Abduction
Adduction
Intortion
Extorsion

Question 25

Action of medial rectus

Answer 25

Adduction

Question 26

Action of lateral rectus

Answer 26

Abduction

Question 27

Action of superior rectus

Answer 27

1. Elevation 2. Adduction 3. Intorsion

Question 28

Action of inferior rectus

Answer 28

1. Depression 2. Adduction 3. Extorsion

Question 29

Action of superior oblique

Answer 29

1. Intorsion 2. Depression 3. Abduction

Question 30

Action of inferior oblique

Answer 30

1. Extorsion 2. Elevation 3. Abduction

Question 31

Neumonic to remember some movements of eye muscles

Answer 31

RADSIN - recti ADductors - Superior INtortors

Question 32

Two types of squint

Answer 32

Esotropia | Exotropia

Question 33

What is esotropia?

Answer 33

Manifest convergent squint

Question 34

What is exotropia?

Answer 34

Manifest divergent squint

Question 35

What is another name for squint?

Answer 35

Strabismus

Question 36

Functional consequences of squint

Answer 36

Amblyopia | Diplopia

Question 37

What is amblyopia?

Answer 37

Lazy eye

Question 38

What is diplopia?

Answer 38

Double vision

Question 39

Pathology of amblyopia

Answer 39

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

Question 40

What is your visual field?

Answer 40

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

Question 41

How do you test the visual field?

Answer 41

``` Confrontation test (outpatient screening) Automated periphery ```

Question 42

How do you test visual acuity?

Answer 42

Reading a chart

Question 43

How are images from your visual field formed?

Answer 43

Formed upside down and inverted into your retina

Question 44

Describe the visual pathway

Answer 44

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

Question 45

What does the optic tract consist of?

Answer 45

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

Question 46

Where do the fibres from the optic tract synapse?

Answer 46

Lateral Geniculate body (LGB) of the thalamus

Question 47

Where is the primary visual cortex found in the brain?

Answer 47

Occipital lobe | Area 17

Question 48

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

Answer 48

Blindness in one eye

Question 49

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

Answer 49

Bitemporal hemianopia

Question 50

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

Answer 50

Contralateral homonymous hemianopia

Question 51

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

Answer 51

Contralateral homonymous hemianopia

Question 52

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

Answer 52

Parasympathetic | Both pupils constrict

Question 53

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

Answer 53

Sympathetic | Pupils dilate

Question 54

Where do fibres destined to activate the pupillary reflex go?

Answer 54

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

Question 55

What does EWN stand for?

Answer 55

Edinger-Westphal nucleus

Question 56

Efferent limb of the pupillary reflex

Answer 56

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

Question 57

What is the name of pupils having different sizes?

Answer 57

Anisocoria

Question 58

Common causes of absent/abnormal pupillary reflex

Answer 58

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)

Question 59

What is horners syndrome?

Answer 59

Anisocoria due to damage to the sympathetic innervation to the pupil

Question 60

Symptoms of horners syndrome

Answer 60

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

Question 61

What is ptosis?

Answer 61

Drooping of eyelid

Question 62

What is anhidrosis?

Answer 62

Loss of sweating on the effected side