Pratical 2 - station 2 - eye movements & visual field

Question 1

What is the inferior of the eyeball divided into and by what?

Answer 1

Anterior cavity and vitreous chamber

Divided by the lens

Question 2

Where is the anterior cavity?

Answer 2

In front of the lens

Question 3

What can the anterior cavity be divided into?

Answer 3

Anterior chamber and the posterior chamber

Question 4

Where is the anterior chamber?

Answer 4

Lies behind the cornea and in front of the iris

Question 5

Where is the posterior chamber?

Answer 5

Behind the iris and in front of the suspensory ligaments and lens

Question 6

What is the purpose of the aqueous humour?

Answer 6

Maintains the shape of the eyeball and supplies oxygen and nutrients to the lens and the cornea
maintains intraocular pressure to maintain eyeball shape and prevent collapse

Question 7

What produces the aqueous humour?

Answer 7

Epithelium over the ciliary body

Question 8

Where does the aqueous humour flow?

Answer 8

Produced from epithelium over ciliary body, flows through pupillary opening into anterior chamber, drains into canals of schlemm where the iris meets the cornea

Question 9

What are the canals of Schlemm and where are they?

Answer 9

Modified vein set

around rim of anterior chamber in the angle of the eye where iris meet cornea

Question 10

How often is the aqueous humour replaced?

Answer 10

Every 3 hours

Question 11

What does the vitreous body do?

Answer 11

vitreous body - jelly like substance
helping preserve shape of eyeball and maintain focussing precision
keeps retina applied to choroids so even surface is maintained for a sharp image

Question 12

Where is the retina?

Answer 12

Between the choroid and the vitreous body

Question 13

What is the function of the fluid of the vitreous body?

Answer 13

Phagocytes - remove debris so vitreal floaters don’t occur

Question 14

What are vitreal floaters?

Answer 14

Specks or shadows that dart in and out visual field, harmless, more common in elderly

Question 15

What are the 6 extra-ocular eye muscles innervated by?

Answer 15

Lateral rectus - abducens
Superior oblique - trochlear
MR, SR, IF, IO - oculomotor

Question 16

What is the action of the medial rectus and lateral rectus?

Answer 16

Medial rectus - adducts the eyeball

lateral rectus - abducts the eyeball

Question 17

What is the action of the superior and inferior recti muslces?

Answer 17

Elevate and depress the eyeball when it is abducted

Question 18

What is the action of the superior and inferior oblique muscles?

Answer 18

Depress and elevate the eyeball when it is adducted.

Question 19

How do the eyelids close? (which muscles, nerves and action)

Answer 19

levator palpebral muscle (CN III) relaxes
orbicularis oculi (CN VII) contracts

Question 20

What is the action of the levator palpebrae superioris and what happens to the eye if it is damaged?

Answer 20

Elevates superior eyelid

Ptosis - dropping of the eyelid

Question 21

What is the action of the superior rectus, nerve innervates it, what happens to eye if damaged?

Answer 21

Intorsion - elevation and adduction
CN III
If damaged pupil down and out as unopposed action of lateral rectus and superior oblique

Question 22

What is the action of the inferior rectus, nerve innervates it, what happens to eye if damaged?

Answer 22

Extorsion - depression and adduction
CN III
IIf damaged pupil down and out as unopposed action of lateral rectus and superior oblique

Question 23

What is the action of the medial rectus, nerve innervates it, what happens to eye if damaged?

Answer 23

CN III
Adduction
If damaged pupil down and out as unopposed action of lateral rectus and superior oblique

Question 24

What is the action of the inferior oblique, nerve innervates it, what happens to eye if damaged?

Answer 24

CN III
Extorsion - acts with superior rectus to allow elevation
If damaged pupil down and out as unopposed action of lateral rectus and superior oblique

Question 25

What is the action of the superior oblique, nerve innervates it, what happens to eye if damaged?

Answer 25

CN IV Intorsion - acts with inferior rectus to allow depression If damaged get weak downward eye movements so affected eye drifts upwards relative to normal eye as unopposed action of other extra-ocular muscles

Question 26

What is the action of the lateral rectus, nerve innervates it, what happens to eye if damaged?

Answer 26

CN VI Abduction If damaged pupil is adducted as unopposed action of medial rectus

Question 27

What is intorsion and extorsion and why do they occur?

Answer 27

Up and in, down and in | Superior and inferior rectus muscles don't pull directly parallel to axis of eyeball so will pull pupil medially.

Question 28

What are the 4 major pathological conditions which affect the eye?

Answer 28

Cataracts Detached retina Glaucoma Pappiloedema

Question 29

What are cataracts? Cause?

Answer 29

``` Opaqueness of the lens Cloudiness of the lens Congenital defects Persistent exposure to UV aging ```

Question 30

How does a detached retina occur? Why is it bad?

Answer 30

Neural retina torn from pigment epithelium as mechanically unstable Photoreceptors metabolically dependent on pigment contact so must be repaired

Question 31

How does surgical repair of detached retina help?

Answer 31

Prevents further increase in detachment area but detached area won't regain function

Question 32

What is glaucoma? How does it occur?

Answer 32

Most common cause of blindness | Aqueous humour build up in anterior eye chamber as canal of Schlemm (scleral venous sinus) blocked

Question 33

Effects of glaucoma

Answer 33

Causes intraocular pressure to increase and fluid compresses on lens into vitreous humour so retinal neurons and blood supply compressed producing ischaemia Mild to irreversible visual impairment from persistent pressure

Question 34

What is papilloedema?

Answer 34

Swelling of the optic disc (papilla) as increased CSF pressure and raised intracranial pressure slowing venous return from retina as compresses on optic nerve and vessels

Question 35

What is papilloedema a sign of?

Answer 35

Raised intracranial pressure - seen in neurological examination of eye and is bilateral

Question 36

What is the effect of papilloedema?

Answer 36

if left untreated pressure increases so constricts retinal ganglion cell axons so can lead to blindness Swelling at constriction leads to disk margin becoming blurred and optic cup lost Papilla may protrude into eye if papilla pressure increases

Question 37

Which structure is immediately posterior to the optic chiasm?

Answer 37

Pituitary gland

Question 38

Which bone is the optic canal found in?

Answer 38

Sphenoid bone

Question 39

Where do the axons from the back of the eyeball cross?

Answer 39

X shaped optic chiasm

Question 40

What fibres do optic tracts contain?

Answer 40

From lateral (temporal) retina of eye on the same side and nasal retina from opposite side (all info. from same half of visual field)

Question 41

Where do the paired optic tracts send axons?

Answer 41

Sweep posteriorly and send axons to synapse in the lateral geniculate nucleus of the thalamus

Question 42

Where do the axons project form the lateral geniculate nucleus of the thalamus?

Answer 42

Through the internal capsule to form the optic radiations and project to the primary visual cortex in the occipital lobe

Question 43

What happens in the primary visual cortex?

Answer 43

Conscious perception of visual images

Question 44

What is the superior colliculus?

Answer 44

Visual reflex centre controlling extrinsic eye muscles | some fibres from optic tracts sent here

Question 45

What is the pretectal nuclei?

Answer 45

Mediates papillary light reflexes | some fibres from optic tracts sent here

Question 46

What field defect is there if there is a lesion to the partial optic nerve?

Answer 46

Ipsilateral scotoma

Question 47

What field defect is there if there is a lesion to the complete optic nerve?

Answer 47

Monocular blindness in that eye

Question 48

What field defect is there if there is a lesion to the optic chiasm?

Answer 48

Bitemporal hemianopia

Question 49

What field defect is there if there is a lesion to the optic tract?

Answer 49

Homonymous hemianopia

Question 50

What field defect is there if there is a lesion to the Meyer's loop?

Answer 50

Homonymous upper quadrantanopia

Question 51

What field defect is there if there is a lesion to the optic radiation?

Answer 51

Homonymous hemianopia

Question 52

What field defect is there if there is a lesion to the visual cortex (medial)?

Answer 52

Homonymous hemianopia

Question 53

What field defect is there if there is a lesion to the visual cortex (lateral-macular)?

Answer 53

Bilateral central scotoma

Question 54

Define hemianopia?

Answer 54

Blindness over half the field of vision