Lecture 5 - Retina And Central Visual Pathways

Question 1

What is the outermost tough layer roof the eye?

Answer 1

Sclera

Question 2

What are some components of the retina?

Answer 2

Pigmented layer
Photoreceptor cells
Bipolar cells
Horizontal cells

Question 3

What is the function of the pigmented layer of the retina?

Answer 3

Helps absorb excessive light preventing overstimulation of the optic nerve

They anchor photoreceptors

Question 4

What is an an example of a condition that has problems with the pigmented layer of the retina?

Answer 4

Albinism

Question 5

What are the 2 types of photoreceptor cells?

Answer 5

Rods
Cones

Question 6

What is the function of the rods?

Answer 6

Black and white night vision

Question 7

What is the function of cones?

Answer 7

Colours and light

Question 8

What is the function of horizontal cells in the retina?

Answer 8

Lateral inhibition of photoreceptors either side of the activated photoreceptor preventing excess signals being sent to the brain

Question 9

What is the function of bipolar cells in the retina?

Answer 9

Connect photoreceptors to axons

Question 10

What artery supplies the retina with blood?

What is this a branch of?

What is this a branch of?

Answer 10

Central retinal artery

Ophthalmic artery

Ophthalmic artery branches from the internal carotid artery

Question 11

What disease can fundoscopy reveal?

Answer 11

Hypertensive retinopathy

Diabetic retinopathy

Macular degeneration

Potential meningitis so can see papilloedmea

Question 12

What blood vessel is occluded if a patient describes a curtain coming down on their vision?

What is this sign called?

Answer 12

Central retinal artery

Amaurosis fugax

Question 13

Go to the last slide and label the retina (1):

Answer 13

1 = fovea
2 = macula
3 = central retinal artery
4 = central retinal vein
5 = optic disc

Question 14

What is the name of the specialist technique used to visualise the layers of the retina?

Answer 14

Optical coherence tomography (OCT)

Question 15

What are the 2 types of visual field?

Answer 15

Temporal visual field
Nasal visual field

Question 16

What are the 2 types of retinal fibres in the optic nerve?

Answer 16

Nasal retinal fibres
Temporal retinal fibres

Question 17

What retinal fibres are responsible for the nasal visual field?

Answer 17

Temporal fibres (since eye is a pinhole and inorder for light from the nasal field to hit the retina it must hit temporal fibres)

Question 18

What retinal fibres are responsible for the temporal visual field?

Answer 18

Nasal fibres (for light to be detected from the temporal field it must come in and hit the nasal fibres)

Question 19

How do the nasal fibres and temporal fibres differ in the way that they travel once they reach the optic chiasm?

Answer 19

Nasal fibres decussate and cross sides
Temporal fibres stay on the same side

Question 20

What part of the brain do the nasal and temporal retinal fibres travel to following the optic chiasm?

Answer 20

Lateral Geniculate nucleus in the thalamus

Question 21

What is the name of the structure following the optic chiasm?

Answer 21

Optic tract

Question 22

What fibres (specifically which sides do the fibres come from) are contained within an optic tract?

Right optic tract

Answer 22

Ipsilateral (right) superior and inferior temporal fibres

Contralateral (left) superior and inferior nasal fibres

Question 23

What are optic radiations?

Answer 23

The temporal and nasal fibres travelling on from the lateral geniculate nucleus to the primary visual cortex

Question 24

What are the 2 different types of optic radiation?

Answer 24

Superior optic radiations

Inferior optic radiations

Question 25

What lobe of the brain do the superior optic radiations travel through to reach the primary motor cortex?

Answer 25

Parietal lobe

Question 26

What lobe of the brain do the inferior optic radiations travel through to reach the primary visual cortex?

Answer 26

Temporal lobe

Question 27

Go to the last slide and draw tthe retinal fibres and their pathways:

Question 28

How are visual field defects named?

Answer 28

Named after the part of the vision that has been lot not where the lesion is located

Question 29

What are the names of all the structures running from the retinal fibres to the end?

Answer 29

Nasal and retinal fibres Optic nerve Optic chiasm Optic tract Lateral geniculate nucleus Optic radiations (superior and inferior) Primary visual cortex

Question 30

What is a Scotoma?

Answer 30

Localised defect in retina causing a small patch of visual loss

Question 31

What type of vision do we have? What is it good for?

Answer 31

Binocular vision Good for depth perception

Question 32

What type of visual defect is caused by an optic nerve lesion?

Answer 32

Monocular blindness

Question 33

What fibres are affected in a left sided optic nerve lesion casuing monocular blindness?

Answer 33

Temporal and nasal fibres on the Ipsilateral side (left) Leads to Ipsilateral loss of temporal and nasal visual fields

Question 34

What type of visual loss is caused by a lesion at the optic chiasm?

Answer 34

Bitemporal hemianopia

Question 35

What fibres are affected in an optic chiasm lesion leading to Bitemporal hemianopia?

Answer 35

The nasal fibres on both sides leading to both temporal visual fields being lost

Question 36

What condition often leads to Bitemporal hemianopia?

Answer 36

Pituitary adenoma

Question 37

What visual field defect occurs as a result of a lesion in the optic tract?

Answer 37

Homonomous hemianopia

Question 38

What is homonomous hemianopia (optic tract lesion)? What fields are lost? What fibres are affected?

Answer 38

When the visual fields on the same side of thh eye are lost (right optic tract lesion means right side of both eyes visual fields are lost) Ipsilateral temporal fibres damaged Contralateral nasal fibres damaged So Ipsilateral nasal field gone Contralateral temporal field gone

Question 39

What visual fields are lost with left sided homonomous hemianopia?

Answer 39

Left eyes temporal field and right eyes nasal field Right optic tract must be damaged

Question 40

What must be damaged if a patient has visual loss in quadrants?

Answer 40

Optic radiations

Question 41

What is responsible for the superior visual field (quadrant)?

Answer 41

Inferior optic radiations

Question 42

What is responsible for the inferior visual field (quadrant)?

Answer 42

Superior optic raiations

Question 43

What condition would be caused by damage to the right superior optic radiation?

Answer 43

So damage to the superior right temporal fibre+ damage to superior Left nasal fibre So loss of vision in the INFERIOR right Nasal visual field and INFERIOR temporal visual field on the left Called Homonomous inferior quadrantanopia

Question 44

What part of the brain does the superior optic radiation travel through?

Answer 44

Parietal lobe

Question 45

What visual field defect is produced by a lesion in the inferior optic radiation?

Answer 45

Homonomous superior quadrantopia Superior nasal field on Ipsilateral side lost Superior temporal field lost on Contralateral side

Question 46

What conditions often lead to both superior and inferior radiations being damaged? Which blood vessel?

Answer 46

Stroke Middle cerebral artery

Question 47

What visual field defect is caused by a stroke due to a middle cerebral artery occlusion damaging both the superior and inferior radiations on the same side?

Answer 47

Homonomous hemianopia

Question 48

What does occlusion of the posterior cerbral artery cause to the vision?

Answer 48

Contralateral homonomous hemianopia with macular sparing

Question 49

Why does macular sparring occur if a stroke is caused by the posterior cerbral artery?

Answer 49

It has a dual blood supply since it still receives blood from the middle cerebral artery

Question 50

What is the accommodation reflex?

Answer 50

Where you are able to focus on nearby objects

Question 51

What is the afferent and efferent for the accommodation reflex?

Answer 51

Afferent = optic nerve Efferent = occulmotor nerve

Question 52

What are the 3 Cs of the accomodation reflex?

Answer 52

Convergence of eyes Constriction of pupils Convexity of lens to inc refractive power

Question 53

What is responsible for convergin the eyes in the accomadtion reflex?

Answer 53

Medial Rectus

Question 54

What is responsible for constriction of the pupils in the accomodation reflex?

Answer 54

Constrictor papillae

Question 55

What is responsible for fattening the lens in the accomadtion reflex??

Answer 55

Ciliary muscle

Question 56

What part of the brain processes in the accomadtion reflex?

Answer 56

Visual cortex via the lateral geniculate neucles Then to oculomotr and edinger Westphal nuclei

Question 57

What is the pathway for the light reflex?

Answer 57

Light Optic nerve Pre-tectal nucleus Then to both edinger westphal nuclei (parasympathic ganglionics) Then to occulmotor nerve (ciliary ganglion) then sphincter pupillae