Physiology Of Vitreous Flashcards Preview

Ocular Phys Block 12 > Physiology Of Vitreous > Flashcards

Flashcards in Physiology Of Vitreous Deck (34)
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1

Largest organ of the eye

Vitreous

2

Vitreous transmits _____ of light

90%

3

Location of vitreous

Between lens and the retina

4

3 zones of the vitreous

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

5

Vitreous attachment to the retina

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

6

Vitreous base

-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

7

What is the strongest vitreal attachment to the retina

Vitreal base at the ora serrata

8

Wiegers ligament (rettrolental ligament)

-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

9

Peripapillary adehsion of vitreous

-around the edge of the optic disc
-medium attachment
-declined with aging

Weiss ring in vitreal detachment

10

Macular and peripheral retinal attachment of vitreous

-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

11

Composition of vitreous

-water major component
-collagen type II
-HA
-vitreal cells
-vitamin C

Does have other substances too

12

Vitreous collagen fibers and HA

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

13

Hyalocytes

-majority
-synthesize glycoproteins for the collagen fibrils
-synthesize HA

14

What cells synthesize HA

Hyalocytes

15

Vitreal cells

Hyalocytes
Fibrocytes
Macrophages

16

Vitreous functions

Support for retina
Diffusion barrier
Metabolic barrier
Transparency

17

Support function of vitreous

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

18

Posterior vitreous detachment (PVD)

-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

Most common pathology of vitreous

PVD

20

Macular edema

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

21

Causes of macular edema

Retinal ischemia
Vitreal traction

22

Diffusion barrier function of vitreous

-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

Diffusion in the vitreous

Slow
-bulk flow is limited
-Abx drops cannot pass though the vitreous into the posterior part of the eye

24

Metabolic buffer of vitreous

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

Reservoir for vitamin C (ascorbic acid)

25

Vitreous protection from oxidative damage

High levels of vitamin C

26

Pathological correlation of diffusion barrier nad metabolic buffer of vitreous

In the case of vitrectomy and full PVD

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

27

What can happen in case of vitrectomy or full PVD

-NSC
-reduce neovascularization in the retina
-neovascular glaucoma

28

Transparency of vitreous

-low cxn of structural molecules
-low cxn of soluble proteins
-specific collagen/HA configuration
-blood/vitreous barrier

29

Pathology with vitreous transparency

-synchisis scintillations
-asteroid hyalosis

30

Synchisis scintillations

Accumulation of cholesterol