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OPTM 5032 - Ocular Physiology > Vitreous > Flashcards

Vitreous Flashcards

1
Q

When does the vitreous begin to liquify (consistenty start change)?

A

The day we were born

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2
Q

How much of the vitreous is water?

A

98% water

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3
Q

What is the volume of the vitreous in the eye?

A

80% (largest structure)

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4
Q

How large is the vitreous chamber in a newborn? in an adult?

A

Newborn - 10.5 mm

Adult - 16.5 mm (13 years of ageO

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5
Q

The liquefaction of the vitreous is at 20% by what age? 50%?

A

20% - 18

50% - 80th decade

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6
Q

What are the non-aqueous components of the vitreous?

A

collagen and glucosaminoglycans (GAGs)

(form the vitreous into a viscoelastic gel)

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7
Q

What interactions does the existence of a gel in the vitreous depend on?

A

Interactions between the GAGs and collagen

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8
Q

The vitreous in ____% Type II collagen

A

75%

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9
Q

The vitreous is ~____% type V/XI collagen?

A

10%

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10
Q

The optic cup is occupoed but the ____ ____ in the early stages

A

lens vesicle

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11
Q

As the optic cup grows, the space is filled with? and secreted by?

A

Fibrillar material

Embryonic retina

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12
Q

Later in life, when the hyaloid artery penetrates the optic cup more _____________ ?

A

fibrillar material from blood vessel cells fills the space

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13
Q

The mass of the optic cup in the end is known as?

A

The primary vitreous

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14
Q

The size of the vitreous cavity _____ and the hyaloid vascular system ______ developing the _____ _____

A

Increases

regresses

secondary vitreous

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15
Q

The main hyaloid artery maintains for a period of time and then disappears and leave the _____ _____

A

Cloquet’s canal

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16
Q

Whay os the Cloquet’s canal?

A

A tube of primary vitreous surrounded by secondary vitreous running from the retrolental space to the optic nerve

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17
Q

Zonules are the _____ _____ that are developed from the _____ _____

A

Suspensor fibrils

Fibrillary material

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18
Q

What structures of the lens are termed the tertiary vitreous?

A

Zonules

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19
Q

The mature vitreous body is a _____ ____ that occupies the vitreous cavity

A

transparent gel

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20
Q

The mature vitreous body has what kind of shape except where?

A

spherical except at anterior end which in concave

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21
Q

What is the outermost oart of the vitreous called and what is it divided into?

A

Cortex

Posterior (100 um thick) and Anterior cortex

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22
Q

The vitreous base is __-dimensional and extends aprox. ____ anterior to the ora serrata to ____ posterior to the ora serrata

A

3

2 mm

3mm

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23
Q

Are the collagen fibrils in the base of the vitreous densely or losely packed?

A

Densely

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24
Q

What can the vitreoretinal interface be defined from electron microscopy as?

A

The outer part of the vitreous cortex (posterior hyaloids)

(includes anchroing fibrils of the vitrois body and the ILM of the retina)

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25
Q

The ILM is a retinal strucure that is between __ and __ thick

A

1 and 3 um

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26
Q

The ILM consists mostly of what type of collagen and ______?

A

Type IV collagen and proteoglycans

27
Q

The ILM is considered the what of the Mueller cells?

A

basal lamina

28
Q

Where is the vitrous cortex firmly attached to the ILM?

A

Vitrous base

around optic disc (weiss ring)

at the vessels

In the area surrounding the foveola (diameter of 500um)

29
Q

Through OCT the preretinal strands (from ____ ____) were found in what percent of non-symptomatic cases?

A

posterior cortex

60%

30
Q

The gel structure of the vitreous acts as a barrier against?

A

movement of solutes

31
Q

How do substances in the vitreous move?

A

Diffusion or bulk flow

32
Q

In diffusion, what can be used as a tracer substance?

A

Fluorescein

33
Q

What is bulk flow in the vitreous cavity a result of?

A

Possible pressure gradient from anterior part of eye toward posterior

34
Q

What form of movement is responsible for the movement of large, high molecular weight substances?

A

Bulk Flow

35
Q

What is liquefaction of the vitreous gel structure also known as?

A

Synchysis

36
Q

Where is synchysis most noteable?

A

In the center of the vitreous

37
Q

When the gel structure of the vitreous is dissolved it is replaced with what?

A

Aqueous lacunae

38
Q

What do the aqeous lacunae do over time?

A

Melt together

39
Q

Does the vitreous collagen molecular weight increase or decrease with age? Why?

A

Increases

Because of the formation of new covalent cross-links between peptide chains

40
Q

Why are proteins in the vitreous cross-linked?

A

Because of the Maillard reaction

41
Q

What is the Maillard reaction

A

Formation of a covalent bond between amino groups and glucose leading to insoluble proteins

42
Q

People with what disease tend to see accelerated Maillard reactions?

A

People with Diabetes mellitus (doubled)

43
Q

The normal physiology of the vitreous body can be divided into what four groups?

A
  1. Support function for the retina and filling-up function of the vitreous body cavity
  2. Diffusion barrier between the anterior and the posterior segment of the eye
  3. Metabolic buffer function
  4. Establishment of an unhindered path of light
44
Q

The intact vitreous body protects what?

A

The retina

45
Q

An intact vitreous body, which fills up the entire vitreous cavity may do what for a retinal detachment?

A

May retard or prevent the development of a larger retinal detachment

46
Q

The vitreous body can absord and reduce what>

A

Absorb external forces

Reduce mechanical deformation of the eye globe

47
Q

What can lead to PVD (posterior vitreous detachment)

A

Central degeneration can lead to a collapse of the rest of the vitreous body, which causes the cortex to sink into the center of the vitreous body

48
Q

If there is a stronf attachment between the posterior cortex and the ILM, a PVD can result in what?

A

A retinal tear

49
Q

What is the first step in a rhegamatogenous retinal detachment?

A

retinal tear from PVD

50
Q

PVD can induce ____ on the retina, especially in the ____ region

A

traction

foveal

51
Q

An increase in the passive permeability or decrease in the outward active transport of the blood-retinal barrier may lead to?

A

Macular edema

52
Q

Substances that are liberated from the anterior segment of the eye have difficulting reaching?

A

High concentrations in the posterior part of the eye because diffusion is slow and movement by bulk flow is limited in a gel

53
Q

If the vitreous body is partly removed the exchange between the anterior and pasterior part of the eye is much ___ and ____

A

faster and easier

54
Q

The preretinal oxygen tension is _____ in diabetic patients after vitrectomy, indicating what?

A

improved

increases with faster fluid currents

55
Q

Can the vitreous act as a metabolic buffer and a reservoir for metabolism of the ciliary body and retina?

A

Yes

56
Q

What can supplement the metabolism in the retina, especially in anoxic conditions?

A

Glucose and glycogen

57
Q

Which Vitamin is present in the vitreous body in high concentrations?

A

Vitamin C

58
Q

Vitamin C can act as a reservoir of antioxidants in which situations protecting the retina from?

A

Stress situations

Metabolic and light induced free radicals

59
Q

Retina substances are diluted by diffusining into where?

A

The vitreous

60
Q

The vitreous needs to maintain an ____ ____ which is produced by the low concentration of structural macromolecules

A

optimal transparency

61
Q

Degeneration of the vitrous body interferes with what?

A

The path of light

62
Q

What are some pathological conditions that interfere with transparency?

A

◦Synchysis scintillations
◦Asteroid degeneration
◦Hemorrhages
◦Inflammatory material
◦Fibrous tissue
◦Lack of regression of the hyaloid artery

63
Q

True or False: Although the vitreous body can be removed and almost normal function of the eye will still be maintained, the vitreous body plays an important role in the physiology and pathophysiology of the eye.

A

True

OPTM 5032 - Ocular Physiology (9 decks)

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