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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
What is the bicarbonate in aqueous humour used for
Buffer the H+ produced in the cornea and lens by anaerobic glycolysis
26
Where is aqueous humour produced
Epithelial layer of ciliary body
27
Describe the flow of aqueous humour from where it is produced
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
28
Where is the canal of Schlemm
Iridocorneal angle (angle between the iris and cornea)
29
What causes glaucoma
Imbalance between the rates of secretion and removal of aqueous humour causing raised intra-ocular pressure
30
What type of drug is used in glaucoma
Carbonic anhydrase inhibitors
31
How do carbonic anhydrase inhibitors treat glaucoma
reduce production of aqueous humour to reduce intra-ocular pressure
32
Examples of carbonic anhydrase inhibitors
Dorzolamide Acetazolomide
33
how is signal transmitted from the retina to the brain
Photoreceptors -> bipolar cells -> ganglion cells
34
What other cells are responsible for signal transmission from the retina to brain
Horizontal cells Amacrine cells
35
What are horizontal cells
Lateral connection between synapse of photoreceptor cells and bipolar cells
36
Function of horizontal cells
They receive input from photoreceptors and project to other photoreceptors and bipolar cells
37
What are amacrine cells
Lateral connection between synapses of bipolar and ganglion cells
38
Function of amacrine cells
Receive input from bipolar cells and project it to other bipolar cells and ganglion cells
39
Types of photoreceptors
Rods Cones
40
How do photoreceptors create a signal
Via phototransduction - conversion of light into electrical potential
41
How does phototransduction occur in photoreceptors
Light exposure causes membrane potential of photoreceptors to hyperpolarize
42
How does light exposure cause the hyperpolarisation of photoreceptor cells
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
What molecule is stimulated by light stimulation and triggers the subsequent dark current
Rhodopsin
44
Describe how the stimulation of rhodopsin leads to hyperpolarisation of the photoreceptors
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
What is visual acuity
Ability to distinguish 2 nearby points
46
Visual acuity is determined by
Photoreceptor spacing Refractive power
47
Why can we only see blurry images in the dark
Due to low visual acuity caused by high convergence in rod system Large spacing of rods
48
What allows colour vision
Different opsins in cone
49
Difference between rods and cones
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
Innate immunity of the eye
Blink reflex Chemical properties in tear film Immune cells in the eye
51
Layers of the tear film
Lipid layer Aqueous layer Mucin layer
52
How does blink reflex provide immune defence
Flushes the substance / pathogen away Mucous layer is anti-adhesive
53
What are the chemicals in tears that protect against pathogens
Lysozymes Secretory IgA tear lipids (antibacterial effect) Cytokines that recruit immune cells
54
Immune cells in the eye
Neutrophils Macrophages Conjunctival mast cells
55
What is the main antigen presenting cell at the eye surface
Langerhan cells
56
Where are langerhan cells mostly located at
Corneo-scleral limbus (junction between cornea and sclera)
57
Which part of cornea are langerhan cells present in
Peripheral cornea (but not a lot)
58
Langerhan cells are not found in
Central 1/3 of cornea
59
Why can other mucosal diseases affect the conjunctiva
Because it has mucosa associated lymphoid tissue - a network of lymphoid tissue covering different mucosal membranes
60
Which part of the eye is the only part with lymphatic drainage
Conjunctiva
61
Immune features of conjunctiva
Lymphatic drainage MALT Presence of APC, T cells, IgA secreting plasma cells Presence of Macrophages, langerhan cells and mast cells
62
What circulate around the MALT frequently
Langerhan cells Macrophages Mast cells
63
Why is cornea and sclera down regulated immune environment
No lymphatics / lymphoid tissue Relatively less APC Langerhan cells only in peripheral cornea
64
What immune features does the lacrimal gland have
IgA secreting plasma cells CD8+ T cells
65
What immune feature does the lacrimal drainage system have
MALT
66
Besides from cornea and sclera, which other part of the eye is also a down regulated immune environment
Retina Choroid Vitreous humour
67
What does immune privilege mean
Sites that are able to tolerate the introduction of antigens without causing an inflammatory cascade
68
Which parts of the eye are immune-privileged
Cornea Anterior chamber Lens Vitreous cavity Subretinal space (space between retinal epithelium and photoreceptors)
69
How does immune privilege occur
lack of lymphatic drainage / blood Lack of APC Immunosuppressive molecules Blood tissue barrier Anterior chamber immune deviation
70
Why is immune privilege beneficial
It protects these structures in the eye from ocular inflammation
71
Why do patients who receive corneal transplant require less immunosuppression compared to other organ transplants
Due to immune privilege of the cornea
72
How does lack of lymphatic drainage and blood allow immune privilege
Prevents APCs from coming in Prevents antigenic information from coming in
73
What is an disadvantage of immune privilege of the eye
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
What condition is an example of disadvantage of immune privilege of the eye
Sympathetic ophthalmia
75
What causes sympathetic ophthalmia
Autoimmune reaction to ocular antigens exposed after injury / surgery

Y2 Ophthalmology (8 decks)

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