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Y2 Ophthalmology > Week 1 > Flashcards

Week 1 Flashcards

1
Q

What is cerebrospinal fluid

A

Clear colourless liquid composed mostly of water but also contains amino acids and ions

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2
Q

What produces CSF

A

Secretory epithelium of choroid plexus

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3
Q

How much CSF is produced per day

A

500-600ml

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4
Q

Where is the choroid plexus located

A

Ventricles in brain

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5
Q

Describe the flow of CSF

A

Formed in ventricles by epithelium of choroid plexus
Circulates around the subarachnoid space
Drain into venous system

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6
Q

The CSF circulate around different ventricles. Describe the flow.

A
  1. CSF produced by choroid plexus in each lateral ventricle
  2. Flows to third ventricle through inter ventricular foramina
  3. More CSF added by choroid plexus in roof of third ventricle
  4. CSF then flows through cerebral aqueduct to reach into the fourth ventricle
  5. Choroid plexus of fourth ventricle adds more CSF
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7
Q

How does CSF enter subarachnoid space

A

Through 3 openings in the roof of fourth ventricle

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8
Q

What are the 3 openings of fourth ventricle that allows CSF to pass into subarachnoid space

A

1 median aperture
2 lateral apertures

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9
Q

Function of CSF

A
  1. mechanical protection
  2. homeostatic funciton
  3. Medium for exchange of nutrients and waste between blood and brain
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10
Q

How does CSF produce mechanical protection

A

It is a shock absorbing medium

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11
Q

How does CSF produce homeostatic function

A

pH of CSF affects pulmonary ventilation and cerebral blood flow
Transports hormones

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12
Q

How is CSF secreted

A

Due to transport of movement of ions, drawing water in

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13
Q

What ventricles are there in the brain

A

Lateral ventricle
Third ventricle
Fourth ventricle

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14
Q

How are the ventricles connected

A

Foramen of Monroe
Cerebral aqueduct (aqueduct of sylvius)
Foramen of Magendie
Foramina of Luschka

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15
Q

If a drug wants to be used for the nervous system, what does it must be able to do

A

Cross the Blood brain barrier

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16
Q

Where is the blood brain barrier

A

Endothelial cells in brain capillaries are sites of BBB

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17
Q

Do all parts of brain have BBB

A

No

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18
Q

What is hydrocephalus

A

Accumulation of CSF in the ventricular system or around the brain causing enlargement of ventricles and increase in intracranial pressure

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19
Q

Increase in intracranial pressure can cause

A

Headache
Visual disturbances due to papilloedema

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20
Q

What is papilloedema

A

Swelling of optic disc due to increased intracranial pressure

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21
Q

How does the increase in intracranial pressure transmit to the optic disc

A

Increase in intracranial pressure transmits to subarachnoid space surrounding optic nerve
The space contains CSF as well

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22
Q

Symptoms of papilloedema

A

Enlarged blind spot
Blurring of vision
Visual obscurations
Loss of vision

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23
Q

What fluid is present in the circulatory system of the eye

A

Aqueous humour

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24
Q

What does the aqueous humour contain

A

Oxygen
Metabolites
Bicarbonate

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25
Q

What is the bicarbonate in aqueous humour used for

A

Buffer the H+ produced in the cornea and lens by anaerobic glycolysis

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26
Q

Where is aqueous humour produced

A

Epithelial layer of ciliary body

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27
Q

Describe the flow of aqueous humour from where it is produced

A
  1. Aqueous humour is produced by the ciliary body and secreted into posterior chamber
  2. It then flows into the anterior chamber
  3. Then drains into canal of Schlemm to drain into scleral venous sinus
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28
Q

Where is the canal of Schlemm

A

Iridocorneal angle (angle between the iris and cornea)

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29
Q

What causes glaucoma

A

Imbalance between the rates of secretion and removal of aqueous humour causing raised intra-ocular pressure

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30
Q

What type of drug is used in glaucoma

A

Carbonic anhydrase inhibitors

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31
Q

How do carbonic anhydrase inhibitors treat glaucoma

A

reduce production of aqueous humour to reduce intra-ocular pressure

32
Q

Examples of carbonic anhydrase inhibitors

A

Dorzolamide
Acetazolomide

33
Q

how is signal transmitted from the retina to the brain

A

Photoreceptors -> bipolar cells -> ganglion cells

34
Q

What other cells are responsible for signal transmission from the retina to brain

A

Horizontal cells
Amacrine cells

35
Q

What are horizontal cells

A

Lateral connection between synapse of photoreceptor cells and bipolar cells

36
Q

Function of horizontal cells

A

They receive input from photoreceptors and project to other photoreceptors and bipolar cells

37
Q

What are amacrine cells

A

Lateral connection between synapses of bipolar and ganglion cells

38
Q

Function of amacrine cells

A

Receive input from bipolar cells and project it to other bipolar cells and ganglion cells

39
Q

Types of photoreceptors

A

Rods
Cones

40
Q

How do photoreceptors create a signal

A

Via phototransduction - conversion of light into electrical potential

41
Q

How does phototransduction occur in photoreceptors

A

Light exposure causes membrane potential of photoreceptors to hyperpolarize

42
Q

How does light exposure cause the hyperpolarisation of photoreceptor cells

A

Due to closing of cGMP-gated Na+ channel = dark current
The change in Na+ signals the brain to perceive objects in the visual field

43
Q

What molecule is stimulated by light stimulation and triggers the subsequent dark current

A

Rhodopsin

44
Q

Describe how the stimulation of rhodopsin leads to hyperpolarisation of the photoreceptors

A
  1. light stimulation of rhodopsin leads to activation of transducin
  2. transducin activates cGMP phosphodiesterase (PDE
  3. cGMP PDE hydrolyses cGMP
  4. Less cGMP = closure of cGPMP- gated Na+ channels
  5. less Na+ entry = hyperpolarization
45
Q

What is visual acuity

A

Ability to distinguish 2 nearby points

46
Q

Visual acuity is determined by

A

Photoreceptor spacing
Refractive power

47
Q

Why can we only see blurry images in the dark

A

Due to low visual acuity caused by high convergence in rod system

Large spacing of rods

48
Q

What allows colour vision

A

Different opsins in cone

49
Q

Difference between rods and cones

A

Rods
- no colour
- at peripheral of retina
- high convergence
- low visual acuity
- high light sensitivity

Cones
- colour
- at central of retina
- low convergence
- high visual acuity
- low light sensitivity

50
Q

Innate immunity of the eye

A

Blink reflex
Chemical properties in tear film
Immune cells in the eye

51
Q

Layers of the tear film

A

Lipid layer
Aqueous layer
Mucin layer

52
Q

How does blink reflex provide immune defence

A

Flushes the substance / pathogen away
Mucous layer is anti-adhesive

53
Q

What are the chemicals in tears that protect against pathogens

A

Lysozymes
Secretory IgA
tear lipids (antibacterial effect)
Cytokines that recruit immune cells

54
Q

Immune cells in the eye

A

Neutrophils
Macrophages
Conjunctival mast cells

55
Q

What is the main antigen presenting cell at the eye surface

A

Langerhan cells

56
Q

Where are langerhan cells mostly located at

A

Corneo-scleral limbus (junction between cornea and sclera)

57
Q

Which part of cornea are langerhan cells present in

A

Peripheral cornea (but not a lot)

58
Q

Langerhan cells are not found in

A

Central 1/3 of cornea

59
Q

Why can other mucosal diseases affect the conjunctiva

A

Because it has mucosa associated lymphoid tissue - a network of lymphoid tissue covering different mucosal membranes

60
Q

Which part of the eye is the only part with lymphatic drainage

A

Conjunctiva

61
Q

Immune features of conjunctiva

A

Lymphatic drainage
MALT
Presence of APC, T cells, IgA secreting plasma cells
Presence of Macrophages, langerhan cells and mast cells

62
Q

What circulate around the MALT frequently

A

Langerhan cells
Macrophages
Mast cells

63
Q

Why is cornea and sclera down regulated immune environment

A

No lymphatics / lymphoid tissue
Relatively less APC
Langerhan cells only in peripheral cornea

64
Q

What immune features does the lacrimal gland have

A

IgA secreting plasma cells
CD8+ T cells

65
Q

What immune feature does the lacrimal drainage system have

A

MALT

66
Q

Besides from cornea and sclera, which other part of the eye is also a down regulated immune environment

A

Retina
Choroid
Vitreous humour

67
Q

What does immune privilege mean

A

Sites that are able to tolerate the introduction of antigens without causing an inflammatory cascade

68
Q

Which parts of the eye are immune-privileged

A

Cornea
Anterior chamber
Lens
Vitreous cavity
Subretinal space (space between retinal epithelium and photoreceptors)

69
Q

How does immune privilege occur

A

lack of lymphatic drainage / blood
Lack of APC
Immunosuppressive molecules
Blood tissue barrier
Anterior chamber immune deviation

70
Q

Why is immune privilege beneficial

A

It protects these structures in the eye from ocular inflammation

71
Q

Why do patients who receive corneal transplant require less immunosuppression compared to other organ transplants

A

Due to immune privilege of the cornea

72
Q

How does lack of lymphatic drainage and blood allow immune privilege

A

Prevents APCs from coming in
Prevents antigenic information from coming in

73
Q

What is an disadvantage of immune privilege of the eye

A

Because the immune system of the eye is separated from the systemic immune system, the eye has a higher chance of developing autoimmune reaction to an antigen that the systemic immune system has already tolerated (= the eye immune system does not know this antigen is not harmful because the systemic immune system cannot communicate with it)

74
Q

What condition is an example of disadvantage of immune privilege of the eye

A

Sympathetic ophthalmia

75
Q

What causes sympathetic ophthalmia

A

Autoimmune reaction to ocular antigens exposed after injury / surgery

Y2 Ophthalmology (8 decks)

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