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Neural Biology 1 > aqueous and vitreous > Flashcards

aqueous and vitreous Flashcards

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1
Q

where is the aqueous humour ?

A
  • in the anterior segment ( in front of iris (anterior )and behind iris (posterior chambers ) filled with aqueous humour
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2
Q

where is the vitreous humour ?

A
  • vitreous cavity filled with vitreous humour
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3
Q

what colour is the aqueous humour ?

A

normally , a clear , colourless fluid

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4
Q

where is the aqueous humour derived from?

A
  • derived from blood plasma
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5
Q

what are the characteristics of aqueous humour ?

A
  • produced and drained continuously

- in constant motion

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6
Q

what is the function of the aqueous humour ?

A
  • provides nutrients to lens , cornea and trabecular meshwork
  • create a lot of lactic acid due to on going metabolism
  • removes waste products of metabolism
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7
Q

what is the similarity between blood plasma and aqueous humour ?

A
  • glucose concentration

- ionic concentration

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8
Q

what is the difference between blood plasma and aqueous humour ?

A

aqueous humour has no protein unlike plasma , this is because proteins are big molecules and would scatter a lot of light

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9
Q

where is the aqueous humour produced ?

A

produced by the ciliary body which is adjacent to the lens and then it flows through the pupil into the anterior chamber where it circulates

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10
Q

where is aqueous humour drained ?

A

drains at the angle formed between the iris and the periphery of the cornea

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11
Q

what is glaucoma ?

A

aqueous pressure rises and it causes damage to the nerve within retina and thus leads to loss of vision

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12
Q

how does aqueous humour generate intra-ocular pressure ?

A

aqueous humour inflates the globe and generates IOP

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13
Q

what is IOP determined by ?

A
  • IOP is determined by the balance between aqueous production and drainage
  • if aqueous isn’t draining quick enough the pressure would rise
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14
Q

why do we need an intra-ocular pressure ?

A

maintain optimal flow rate adequate IOP necessary for maintaining structural integrity and normal optimal function of eye

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15
Q

what would a abnormal IOP lead to ?

A

abnormal IOP leads to glaucoma

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16
Q

how to treat glaucoma ?

A

pharmacological suppression of aqueous secretion or enhanced drainage is mainstay of glaucoma treatment

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17
Q

how much does the vitreous humour fill of the inferior volume of eye ?

A

vitreous humour fills 80% of the inferior volume of the eye ( 4ml volume )

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18
Q

what are the function of vitreous humour ?

A
  • helps maintain shape of eye
  • supports retinal attachment
  • storage area for metabolites for retina and lens
  • viscoelastic - i.e. shock absorber protecting retinal tissue during eye movement
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19
Q

what are the characteristics of the vitreous humour ?

A
  • has structure ( fine collagen fibrils
  • not always transparent
  • is not inert e.g. ‘ floaters’
20
Q

what are 3 fundamental components of the vitreous humour ?

A
  • some collagen fibres
    ( mainly type ll but some lv and lx )
-  proteoglycans 
hyaluronic acid ( glysosaminoglycan ) just sugar bit without the protein
  • mainly water
21
Q

what is the structure of the vitreous humour ?

A
  • vitreous is widely spaced matrix of collagen fibrils and HA ( hyaluronic acid ) molecules
  • spaces are filled with water molecules , mostly bound to HA
  • produces a gel-like structure
22
Q

explain the chemical analysis of vitreous ?

A

collagen - HA matrix makes up only 1% of vitreous by weight

99% water - constantly replaced by diffusion mainly from aqueous

23
Q

what can collagen fibrils do in the vitreous humour ?

A

collagen fibrils can aggregate and if bundles are large enough produce floaters

24
Q

what happens as you move toward the periphery of the vitreous cavity towards the vitreous cortex ?

A

this is where collagen fibrils tend to predominate in the periphery so much more collagen in edge then in centre

25
Q

what is vitreous cortex ?

A

edge of vitreous

26
Q

what produces HA and collagen ?

A

hyalocytes which also function as phagocytes

27
Q

what happens in the eye development in the early stages of embryological development ?

A
  • there is a vascular connection between the optic nerve and anterior developing part of eye
  • there is a blood vessel called the hyaloid artery which runs from the optic nerve to the lens
  • as eye develops that artery disappears
28
Q

what is canal of cloquet ?

A
  • where the hyaloid artery was during embryological development
29
Q

what are the characteristics of vitreous cortex ?

A
  • 100-200 um mean thickness
  • thicker on anterior surface adjacent to ciliary body and lens
  • thinner adjacent to retina
  • collagen fibrils in vitreous cortex denser than in inner vitreous
  • merges with basement membrane on surface of ciliary body and retina
30
Q

what do we use to look into vitreous ?

A
  • dark field illumination
31
Q

what is the hole in the collagenous matrix of vitreous ?

A
  • hole in the vitreous cortex where optic nerve is

- hole in vitreous cortex where you got the macular

32
Q

what kind of attachments does the vitreous have ?

A
  • attachment to optic nerve
  • attachment to lens
  • attachment adjacent to macula
33
Q

what is the strongest attachment of the vitreous ?

A
  • the vitreous base thats where the vitreous connects with the ciliary body
34
Q

what is the anterior surface of the vitreous ?

A
  • anterior surface of vitreous is a distinct layer of dense collages called anterior hyaloid membrane
35
Q

what is patellar fossa?

A

cup-shaped depression in this anterior hyaloid membrane occupied by posterior surface of lens

36
Q

what happens to the vitreous as we get older ?

A
  • change relates to the relative amounts of gel and liquid compartment of the vitreous liquid compartment
  • vitreous get more watery and gel starts to fall
  • increases liquefaction of gel causes gel to collapse in upon itself so you might see floaters in vision

-

37
Q

what do floaters in vision correspond to ?

A
  • aggregation of collagen fibrils

- collagen fibrils fuse together and form shadow on retina as you get older

38
Q

what is collagen present as in young vitreous ?

A

present as fibrils

39
Q

what is collagen present as in older vitreous ?

A

bundle

40
Q

what is collagen redistribution responsible for ?

A

responsible for liquid fraction increase

41
Q

what is posterior vitreous detachment ?

A
  • gel collapses on it self - gel pulling from back
  • patients can see flashes of light as gel tugs on retina thus generating photopsia
- patients often experience a 
circular floater ( weiss ring ) consisting of avulsed glial tissue from around the optic nerve head
  • vitreal volume is
    unchanged but rearrangement of gel and liquid components
  • detached vitreous can tug on retinal blood vessels and produce haemorrhage
  • common in older eyes
42
Q

what is retinal detachment ?

A
  • posterior vitreal detachment can tear the retina - liquid vitreous can leak behind photoreceptors leading to retinal detachment
  • must dilate pupil and have to exclude retinal detachment
43
Q

what is OCT ?

A

gives cross-section view through the retina

  • you can see a posterior vitreous detachment very clearly on OCT
44
Q

what happens if you get abnormal attachments between the vitreous and the region of retina adjacent to fovea ?

A

it can cause extreme damage to macular and lead to macula hole

45
Q

what is vitreomacular traction ?

A

Vitreomacular traction is a condition in which the vitreous gel has an abnormally strong adhesion to the retina. Over time, the gel tends to pull forward and can cause vessel and retinal distortion causing retinal swelling and decreased vision.

46
Q

what is mittendorf dot ?

A
  • remnant of hyaloid artery

- fragment on posterior surface of lens

47
Q

what is bergmeister’s papilla?

A

remnant of hyaloid artery on otic nerve

Neural Biology 1 (58 decks)

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