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Neurology physiology > Vision > Flashcards

Vision Flashcards

1
Q

List 3 layers of the eye from outer to inner

A

1- Sclera and Cornea
2- Uvea ( choroid , ciliary body , iris )
3- Retina

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2
Q

What is the function of the Sclera

A

1- Protect eye from trauma
2- Maintains intraocular pressure
3- Allows attachment of the extra ocular muscles

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3
Q

What is Glaucoma

A

When pressure in eye is high enough to cause damage

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4
Q

How many extra ocular muscles are there for each eye

A

Six

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5
Q

What is the function of the choroid

A

1- Supplies nutrients and oxygen to outer retina

2- pigment absorbs light

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6
Q

The blood vessels of the retina only supply with Half? what’s happening with the other half

A

The inner half. The outer half is supplied by the underlying choroid

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7
Q

What is the most vascular part of the body

A

The choroid

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8
Q

What is the clinical relevance of the choroid

A

Macular degeneration

- Age related condition affecting the macula , the centre of the retina used for central vision

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9
Q

Wet vs Dry macular degeneration

A

Wet: sheet of vascular tissue comes up from the choroid , grows anteriorly under the retina and then goes into the retina = bleeds and leaks

Dry: Thinning of the macula

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10
Q

80 year old patients comes in with loss of central vision, what is the first though ?

A

Macular degeneration

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11
Q

Causes of Macular degeneration ( risk factors )

A

1- Age
2- SMoking
3- Fam history

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12
Q

What is Myopia

A

Short sightedness

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13
Q

What is Hypermetropia

A

Long sightedness

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14
Q

What is astigmatism

A

Front of the eye , the cornea has an abnormal curvature that is steeper in one axis than another.
Can happen with short or long sightedness

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15
Q

What is the function of the cornea

A

Most of refraction of light occurs at the cornea. At the air tear film interface ( as light passes from air to water medium )

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16
Q

What are the two clinically relevant layers of the cornea

A

1- Epithelium : constantly regenerated

2- Endothelial cells : maintain/prevent dehydration of stroma

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17
Q

What is the clinical relevance of the cornea

A

Corneal abrasion : scratch on the surface of the cornea , in the epithelium –> takes a few days to heal , will be very photophobic until it’s healed

Opaque cornea : needs corneal transplant

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18
Q

When would a cornea under blue light and with orange fluorescent drops show up as green

A

In a corneal abrasion.

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19
Q

Would you need systemic immunosuppression after cornea transplant

A

No because cornea is avascular

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20
Q

What is the function of the iris

A 
Smooth muscles controlling pupil 
1- Sphincter pupillae constricts pupil 
- supplied by PNS 
2- Dilator pupillae dilates pupil 
- supplied by SNS
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21
Q

When SNS is on the pupil dilates or constricts ?

A

Dilates

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22
Q

What is Corner syndrome

A

interruption to sympathetic supply to the eye , causing unopposed parasympathetic stimulation ( constricting )

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23
Q

The front part of the eye is filled with ?

A

Aqueous humour

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24
Q

What produces the aqueous humor

A

The ciliary body

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25
Q

Explain the flow of aqueous humor

A

1- goes between lens and iris
2- into anterior chamber
3- between cornea and iris
4- down through trabecular meshwork

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26
Q

Where is the blockage of aqueous humor in acute glaucoma

A

Between the pupil and iris causing increase in pressure

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27
Q

What is glaucoma

A

Imbalance between rate of production and drainage of aqueous humor = causing raised intraocular pressure

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28
Q

What are the functions of the of the ciliary body

A

1- produce aqueous humor

2- ciliary muscle contracts when we focus on near objects

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29
Q

Process of ciliary muscle contracting when focusing on near objects is called ?

A

Accommodation

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30
Q

What is presbyopia

A

Age related reduction in ability to accommodate , mainly due to lens stiffness

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31
Q

What is the treatment for presbyopia

A

Reading glasses : very focal glasses

32
Q

What is the clinical relevance of the lens

A

Cataract : Lens is opaque/ foggy

33
Q

What is the vitreous humor

A

Found posterior to lens , a hydrated Gell with collagen fibrils.
Attached to retina

34
Q

Any traction to vitreous results in pull on ?

A

Retina

35
Q

What is posterior vitreous detachment

A

Vitreous liquifies & collapses in on itself = pulls on retina , causes symptoms of flashes and floaters

36
Q

What are the two retina layers

A

1- Neural layers : made 9 layers

2- Retinal pigmented epithelium ( RPE )

37
Q

What is the function of the retina ( cones and rods )

A

Rods perceive light intensity ( at periphery )

Cones in the Fovea, in the centre of the macula perceive colour

38
Q

What is the optic disk

A

Where axons form the ganglion cells merge to form the optic nerve.
The blind spots since there’s no photoreceptors there

39
Q

The ophthalmic artery is branch of the ?

A

Internal carotid artery

40
Q

What are the branches of the ophthalmic artery

A

1- Central retinal artsy

41
Q

Explain the course of the central retinal artery

A

Runs beside the central optic vein in the optic nerve. Pierces the eyeball through the lamina cribrosa.
End artery and supplies inner 2/3 of the retina

42
Q

What is the lamina cribrosa

A

A hole ( sieve like thinned area ) in the sclera where the optic nerve goes into the eyeball. Central retinal vessels go through it with the optic nerve into the eyeball.

43
Q

What are the optic disc rim and cup

A

Rim : Where the ganglion cells running towards the optic disk turn 90 degrees to form optic nerve , creates a darker rim around the optic disc

Cup : middle of optic disc that is just bare sclera, thin sieve like part that allows entering of optic nerve & vessels

44
Q

What is the clinical relevance of the central retinal artery

A

The only supply of blood to the retina.

Usually blocked by clot from the internal carotid artery

45
Q

Pale colour of retina indicates what

A

Blockage of blood flow to retina

46
Q

Thinner vessels in the retina are the ?

A

The arteries

47
Q

Clinical features of the macula

A

1- Blood vessels go around it, not through it
2- darker in the middle
3- To the temporal side of the disc

48
Q

Central of the macula is known as the ?

A

Fovea

49
Q

What is a clinical indication of central retinal artery occlusion

A

Cherry red spot :

Pale retina but fovea is very red spot

50
Q

What are the 4 branches of the central retinal artery

A

1- Supertemporal
2- infro temporal
3- inferonasal
4- superonasal

51
Q

Is the fovea vascular or avascular

A

Avascular

52
Q

Where is the capillary network most dense in the retina

A

in the Macula

53
Q

How can raised intracranial pressure be seen in the eye , How will it look like

A

Optic nerve is surrounded by dude matter and arachnoid sheaths so raised ICP will be submitted along the subarachnoid space. Thin walled central vein will be compressed causing congestion and thus papilloedema.

Clinical Features : Contour of disc is indistinct , looks swollen , veins look compressed , red streaks around the discs

54
Q

What branches of the opthalmic artery supply the uveal tract

A

Ciliary arteries :
1- Long posterior ciliary
2- short posterior ciliary
3- Anterior ciliary

55
Q

The components of the uveal tract are

A

Choroid , ciliary body , iris

56
Q

What is the aura serrata

A

anteriorly the retina finishes at the Wavy line called aura serrata . Where you would go through in surgery rather than the retina and damaging it

57
Q

The space between the RPE cells and the photoreceptors is a potential for what

A

Potential to open up , where retinal detachment usually happens. Aka sub retinal space

58
Q

What forms the outer blood retinal barrier

A

The tight junctions of the RPE cells form the barrier

59
Q

The outer blood retinal layer gives the retina ?

A

1- immune protection

2- ability for exchange of substances

60
Q

RPE live in what type of environment

A

Highly oxidative

61
Q

Is oxygen extracted in the choroid

A

Little oxygen is extracted , despite the high blood flow

62
Q

What is a by product of oxidative damage in the RPE

A

Lipofuscin ; orange spots in the eye

63
Q

If not much oxygen is extracted in the choroid what is the purpose of the choroid having a high blood flow

A

Choroid takes away heat from the RPE ( which absorbs light )

64
Q

Explain the visual cycle

A

1- photo of light is absorbed in the protoreceptors by 11-cis retinal
2- results in change in its conformation = bleaching
3- 11 cis-retinal attached to opsin changes to all-trans retinal & free opsin
4- All-trans retinal is dumped to RPE which gives it back to photoreceptors ( recycles )

65
Q

What does the RPE secrete

A

VGEF : vascular endothelial growth factor

66
Q

Excess VGEF can cause what in the retina

A

Leaking from retina , due to too much fenestration of choroid

67
Q

Are ganglion retinal cells myelinated ? What is the condition associated with this ?

A

They are not myelinated.

Myelinated ganglion cells are a congenital condition , doesn’t affect day to day , might have bigger blind spots ?

68
Q

What is an OCT

A

Optical coherence tomography

- imaging of the layers of the eye

69
Q

What is the route of the Optic nerve out of the eye ball

A

Orbital portion of optic nerve goes out of eye ball , passes through optic canal in sphenoid bone , then backwards and upwards to floor of 3rd ventricle. joins other optic nerve to form optic chasm

70
Q

What are the important relations of the optic chasm

A

Laterally : carotid arteries
Inferiorly : pituitary gland
Fibres from the nasal side of eye cross ( temporal view )

71
Q

What is the most common cause of optic chasm problems and what would the signs be

A

Cause : pituitary adenoma

Signs : crossing fibres of nasal side are squeezed causing missing of temporal side vision of each eye

72
Q

What are the optic tracts

A

Emerge from posterior corners of the optic chasm.
Travel posterolaterally.
Most of the fibres synapse in the Lateral geniculate body.
Then go to primary visual cortex via optic radiation

73
Q

Same side of each eye vision being effected is called

A

Homonymous hemianopia

74
Q

Problem with left optic tract/ radiation is known as

A

Right homonymous hemianopia

75
Q

Explain Pupillary light reflex

A

1-in the optic tract : Most fibres synapse at the LGB , but some leave before LGB and synapse at pretetal nucleus
2- goes to Edinger Westphal nucleus of both sides
3- stimulates third cranial nerve to the ciliary ganglion
4- causes contraction of pupil in iris

76
Q

Afferent limb of the light reflex is controlled by with CN

A

CN2 ( optic nerve )

Neurology physiology (9 decks)

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