1. Visual Pathways 1

Question 1

Out of the 2 RGCs, which one crosses at the chiasm and which one stays on the same side?

Answer 1

The axons of nasal RGCs cross as the chiasma and the axons of temporal RGCs stay on the same side.

Question 2

Out of the 2 RGCs, describe where the cells in each look at in terms of receptive feids? For example on the left side- before vs after crossing chiasma?

Answer 2

On the left side: the temporal cells look right visual field and nasal cells look at the left visual field. Hence, once the RGCs cross the chiasma the left eye is looking at the right visual field.

Question 3

Right optic tract get information from RGCs that are looking at which visual field?

Answer 3

Left hemi- field.

Question 4

Majority of RGCs go to?
Where do the rest of RGCs go to?

Answer 4

Majority go to LGN
Rest go to the Tectum and supra- chiasmatic nucleus.

Question 5

Role of Supra- Chiasmatic nucleus?

Answer 5

Light- mediated onset of body rhythms in the morning.

Question 6

Role of pretectum?

Answer 6

Control pupillary light reflex.

Question 7

Superior colliculus, Supra- chiasmatic nucleus (SCN) and Pretectum are reflexive and are involved in secondary visual pathways, explain why?

Answer 7

Because they are not involved in conscious vision.

Question 8

Which pathway is involved in conscious vision?

Answer 8

LGN- Referred to as primary visual pathway.

Question 9

Which cranial nerve is the optic nerve?

Answer 9

CN II

Question 10

What is the reference point of visual fields? This point is also known as?

Answer 10

Fovea- retinal coordinates are determined by this point.
Also known ad: Fixation point

Question 11

What is the lower retina in terms of visual fields?

Answer 11

Lower retina= upper field

Question 12

What is the temporal retina in terms of visual field?

Answer 12

Temporal retina= nasal field

Question 13

Optic disc is temporal or nasal to the fovea?

Answer 13

Nasal

Question 14

Vertebtrae retina is referred to as reversed retina, why?

Answer 14

Because light has to go through all superficial layers of the retina before hitting the RPE (photoreceptors).

Question 15

Horizontal cells integrate information from?

Answer 15

Adjacent photoreceptors
AND generate centre-surround receptive fields in cones.

Question 16

Role of bipolar cells ?

Answer 16

Provide the main pathway from photoreceptors to retinal ganglion cells

Question 17

Bipolar cells vs amacrine cells, which cells have axons?

Answer 17

Bipolar cells have axons, amacrine cells have no axons.

Question 18

RPE is the location where what synapses?
RGCs define what?

Answer 18

Bipolar and amacrine cells synapse. RGCs define visual properties that are then sent to the brain.

Question 19

The brains only contact to the eye is through?

Answer 19

Through axons of RGCs

Question 20

Optic nerve fibres emerge on the surface of the retina and proceed to?

Answer 20

The optic nerve head

Question 21

What is found in the inner nuclear layer of the retina?

Answer 21

Cell bodies and amacrine cells

Question 22

Where is the outer segment of photoreceptors found in the retina?

Answer 22

In the retinal pigment epithelium (RPE).

Question 23

Role of retinal pigment epithelium (RPE) in the retina?

Answer 23

Important for metabolism and disc shredding. It is opaque hence found behind. And it is where Bipolar and Amacrine cells synapse.

Question 24

Why is the retina reversed?

Answer 24

Retinal pigment epithelium is opaque, if it was in the front you would not be able to see anything.

Question 25

Retina has what kind of blood supply?

Answer 25

Dual blood supply, each layer of the retina is supplied differently.

Question 26

What gives the optic nerve stability?

Answer 26

It has some underlying structures that give stability.

Question 27

Optic nerve fibres from axons and RGCs go through the holes in the lamina cribrosa, describe the organisation of fibres that go through the holes

Answer 27

The fibres that go into a given hole are from cells that are adjacent to each other.

Question 28

The fibres that emerge of the optic nerve head are fatter, why? And why are they seen as white?

Answer 28

As fibres are moving to the optic nerve head they are de- myelinated and hence become thicker and hence seen as white.

Question 29

Role of myelin sheath?

Answer 29

It is an insulated later. Role: speeds up propagation of nerve impulses to the brain.

Question 30

In the fovea the inner layers of the retina are excavated, why?

Answer 30

Even though the inner layers of the retina are transparent they do still scatter light. When these layers are absent and you have the highest concentration of photoreceptors, this improves vision. As the fovea is responsible for sharp central vision.

Question 31

Retinal layers end near the border of the optic nerve they are separated from nerve by ring of glial tissues known

Answer 31

Intermediary tissue of Kuhnt.

Question 32

Choroid and sclera are separated from optic nerve by ring of white fibrous tissue containing glia, fibres and some pigments known as

Answer 32

Marginal or border tissue.

Question 33

Optic nerve head has some underlying structures that give it stability- this is stability against pressure, what are this structures?

Answer 33

The intermediary and marginal tissues

Question 34

Does Brunch's membrane and choroidal vascular layer enter the optic nerve head?

Answer 34

Bruch’s membrane extends all the way to the optic nerve, but choroidal vascular layers end some distance from it.

Question 35

What is the role of lamina cibrosa?

Answer 35

A sieve- like structure through which RGC axons come through to the optic nerve and become myelinated.

Question 36

Optic disc is not completely white, why?

Answer 36

Some underlying RGCs.

Question 37

What covers the optic nerve?

Answer 37

Dural sheath- this are the meninges membranes.

Question 38

Is the eye part of the brain or a separate structure?

Answer 38

Eye is part of the brain and it emerges from the brain during early development.

Question 39

Describe the optic nerve head seen in patients with glaucomatous?

Answer 39

Due to increased IOP causes cells to die and results in fewer fibres entering the optic nerve. Hence the cup is seen excavated- due to tissue loss.

Question 40

Why does the cup appear to be more white in patients with glaucomatous?

Answer 40

Due to the unobstructed view of myelinated fibres that leave the optic nerve.

Question 41

In early development the lens is supplied by what structure?

Answer 41

Hyaloid arteries

Question 42

Is Hyaloid arteries seen in adults/ after development?

Answer 42

Some patients may still have this artery and it is normal, it does not impact vision.

Question 43

What is scleral canal?

Answer 43

Opening in the sclera through which the optic nerve will pass.

Question 44

Are all the nerves in the optic nerve myelinated?

Answer 44

Yes

Question 45

What is the beginning point of all the nerves found in the optic nerve head?

Answer 45

Lamina Cribrosa

Question 46

Optic nerve is the extension of?

Answer 46

Brain tissue

Question 47

Nerve fibres are compressed of which 3 fibers?

Answer 47

1. Visual Fibres 2. Pupillary Fibres 3. Centrifugal Fibres

Question 48

Visual Fibres and Pupillary Fibres are from?

Answer 48

Axons of RGCs

Question 49

Visual fibres on to the path to ?

Answer 49

LGN

Question 50

Pupillary fibres go to?

Answer 50

Pretectum

Question 51

Optic nerve is divided into bundles, divided by connective tissues called?

Answer 51

Septa

Question 52

Is septa constant in all places? If not what is the role of this?

Answer 52

No, in places bundles of tissues are divided by glial tissue just before the optic chiasm. This plays an important role in the nasal and temporal crossing of fibres at the chiasm.

Question 53

Large glial septum runs through middle of nerve dividing fibres into?

Answer 53

Ventromedial and dorsolateral portions

Question 54

Optic nerve fibres are surround by?

Answer 54

3 meninges- pia mater, arachnoid and dura mater.

Question 55

What is meant by subdural?

Answer 55

Space under the dura and above arachnoid.

Question 56

What is meant by subarachnoid?

Answer 56

Space below the arachnoid and above the pia.

Question 57

What disease that affects the myelination of the optic nerve

Answer 57

MS (multiple sclerosis)

Question 58

Early signs of MS? (What does the patient notice)

Answer 58

Patients complain vision in 1 eye is darker than the other eye- luminance value changes.

Question 59

Compare Pia matter to dura matter:

Answer 59

Pia matter is the inner most layer this area is highly vascularized. Dura mater is much less vascularized since it provides structural support and is the other most layer.

Question 60

Location of optic chiasm

Answer 60

Optic Chiasm is located at the junction of the anterior wall and floor of the third ventricle. It lies above the pituitary fossa.

Question 61

Optic Chiasm is covered in?

Answer 61

Covered in pia mater and suspended in CSF.

Question 62

Right optic tract mediates information from which field?

Answer 62

Left- hemi feild

Question 63

Optic chiasm is known as the location where?

Answer 63

Where nasal fibres cross

Question 64

Left and right hemi-fields are defined by?

Answer 64

Defined by the vertical meridian

Question 65

Optic tract 1st synapse at?

Answer 65

LGN- that gives rise to radiations

Question 66

LGN project to?

Answer 66

Back brain- visual cortex