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Ocular Phys Block 12 > Physiology Of Vitreous > Flashcards

Physiology Of Vitreous Flashcards

1
Q

Largest organ of the eye

A

Vitreous

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2
Q

Vitreous transmits _____ of light

A

90%

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3
Q

Location of vitreous

A

Between lens and the retina

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4
Q

3 zones of the vitreous

A

Outermost: vitreous cortex (hyaloid cortex)
Center zone: cloquets canal
Intermediate zone: inner to the cortex and surrounds the center canal

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5
Q

Vitreous attachment to the retina

A

Vitreous attached to ILM of retina by the membrane limitans interna (MLI)

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6
Q

Vitreous base

A
  • Located at ora serrata
  • 1.5mm broad annular region
  • attached to NPE of ciliary body and the ILM of the peripheral retina
  • strongest attachment
  • no age declined
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7
Q

What is the strongest vitreal attachment to the retina

A

Vitreal base at the ora serrata

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8
Q

Wiegers ligament (rettrolental ligament)

A
  • between the posterior surface of the lens and the anterior surface of the vitreous
  • firm attachment
  • declined with age
  • creates burgers space on the back of the lens
  • space between vitreous and lens
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9
Q

Peripapillary adehsion of vitreous

A
  • around the edge of the optic disc
  • medium attachment
  • declined with aging

Weiss ring in vitreal detachment

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10
Q

Macular and peripheral retinal attachment of vitreous

A
  • weak attachment
  • findings are controversial for macular attachment
  • some individuals may have an attachment 3-5mm posterior to the vitreous base. Attach to retinal blood vessels
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11
Q

Composition of vitreous

A
  • water major component
  • collagen type II
  • HA
  • vitreal cells
  • vitamin C

Does have other substances too

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12
Q

Vitreous collagen fibers and HA

A

The gel structure of the vitreous results from the arrangement of collagen fibrils suspended in a network of HA

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13
Q

Hyalocytes

A
  • majority
  • synthesize glycoproteins for the collagen fibrils
  • synthesize HA
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14
Q

What cells synthesize HA

A

Hyalocytes

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15
Q

Vitreal cells

A

Hyalocytes
Fibrocytes
Macrophages

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16
Q

Vitreous functions

A

Support for retina
Diffusion barrier
Metabolic barrier
Transparency

17
Q

Support function of vitreous

A
  • prevents retinal detachment
  • reduced mechanical deformation
  • supports lens during trauma
  • decreases transmission of light at 300-350nm
  • mechanical support of limited signicance
18
Q

Posterior vitreous detachment (PVD)

A
  • 10% of eyes have strong vitreous retina attachments
  • vitreous traction can cause retinal tears
  • possibility of vitreous hemorrhage’s
  • high risk of rhegmatogenous retinal detachment

Normal aging process

19
Q

Most common pathology of vitreous

A

PVD

20
Q

Macular edema

A
  • in some cases
  • vitreous-retinal traction
  • increase in passive permeability
  • decrease in active transport across blood retinal barrier
  • increased osmotic pressure
21
Q

Causes of macular edema

A

Retinal ischemia

Vitreal traction

22
Q

Diffusion barrier function of vitreous

A
  • slow diffusion actress vitreous
  • bulk flow is limited across veitrous
  • prevents topically adminstered substance from reaching the retina
  • prevents substances in blood stream from reaching vitreous center
  • no diffusion barrier for small molecules
23
Q

Diffusion in the vitreous

A

Slow

  • bulk flow is limited
  • Abx drops cannot pass though the vitreous into the posterior part of the eye
24
Q

Metabolic buffer of vitreous

A

Contains a lot of substances like glycogen, glucose, nutrients for retinal metabolism

Reservoir for vitamin C (ascorbic acid)

25
Q

Vitreous protection from oxidative damage

A

High levels of vitamin C

26
Q

Pathological correlation of diffusion barrier nad metabolic buffer of vitreous

A

In the case of vitrectomy and full PVD

NSC (nuclear sclerotic cataract)
Reduce neovascularixation in the retina
Neovascular glaucoma

27
Q

What can happen in case of vitrectomy or full PVD

A
  • NSC
  • reduce neovascularization in the retina
  • neovascular glaucoma
28
Q

Transparency of vitreous

A
  • low cxn of structural molecules
  • low cxn of soluble proteins
  • specific collagen/HA configuration
  • blood/vitreous barrier
29
Q

Pathology with vitreous transparency

A
  • synchisis scintillations

- asteroid hyalosis

30
Q

Synchisis scintillations

A

Accumulation of cholesterol

31
Q

Asteroid hyalosis

A

Accumulation of Ca

32
Q

What causes gel structure of vitreous?

A

HA process spacing and support for the collagen

33
Q

What substances maintains high Cxn in vitreous and can be utilized to protect the retina from metabolic and light induced free radicals

A

Vitamin C

34
Q

What are the vitreous functions

A

Provides a transporter medium
Cushion the globe
Storage are of ions and nutrients for the retina and lens

Ocular Phys Block 12 (5 decks)

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