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Eye And Visual Pathways > Vitreous Humor > Flashcards

Vitreous Humor Flashcards

1
Q

What percent if the eye is occupied by vitreous
And was is its volume

A

Approx 80%
And approximately 4.5ml in volume

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2
Q

What is the vitrous humor

A

Gel like substance that fills up the space between lens and retina

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3
Q

Function of hyaloid/ cloquet’s canal

A

Embryonic development of the eye, facilitating transport of nutrients to developing structures

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4
Q

What are the three types of vitreous

A

Central vitreous
Basal vitreous
Vitreous cortex

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5
Q

What is the thickness of vitreous cortex

A

100-300 micrometers

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6
Q

What is the direction of the posterior vitreous cortex

A

Runs parallel to the retina

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7
Q

Which part of retina is the vitreous cortex absent

A

Optic disk

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8
Q

Why is vitreous thinned at the macula

A

For optical clarity

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9
Q

What are the main components of vitreous

A

Water
Soluble proteins
GAGs
Glycoproteins
Electrolytes/ salts

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10
Q

Main properties of vitreous humor

A

Transparency
Highly hydrated gel
Avascular ie lacks blood vessels
Highly viscoelastic
Non compressible

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11
Q

What percentage of vitreous is water

A

More than 98%

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12
Q

Which type of vitreous is not acellular

A

Basal vitreous
Vitreous cortex

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13
Q

What type of cells are found in the vitreous humor

A

Hyalocytes

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14
Q

Function of hyalocytes

A

Synthesis and maintenance of hyaluronic acid

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15
Q

What are the main carbohydrates and, proteins present in vitreous

A

Carbohydrates- glycosaminoglycans (GAGs)
Proteins- collagens

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16
Q

Describe the changes in hyaluronan concentration with age

A

Increases up to 20 years
Constant until 70 years
Increases 70+ years

17
Q

Which part of vitreous contains
1. Lowest hyaluronan
2. Highest hyaluronan

A

Lowest- central vitreous
Highest- posterior vitreous

18
Q

What is the main collagen present in vitreous

A

Collagen II (75%)

19
Q

Where in the vitreous, is the concentration of collagen at
1. Its highest
2. Its lowest

A

Highest- vitreous base
Lowest- central

20
Q

When in the human embryonic life does synthesis of the adult-type vitreous begin

A

Sixth week

21
Q

What is vitreous liquefaction

A

Process in which the gel -like vitreous humor in the eye becomes more liquid/ less gel like in consistency

22
Q

Around 80-90 years old, what percentage of the vitreous gel has turned into liquid

A

50%+

23
Q

What are some mechanisms of vitreous liquefaction

A

Collagen breakdown leads to the loss of structural intergrity
Water content changes
Enzymes- can cause breakdown of structural proteins
Cross linking of proteins

24
Q

What is syneresis

A

Contracting and shrinkage of the gel, leading to the release of fluid and changes in the vitreous structure

25
Q

How does liquefaction lead to posterior vitreous detachment

A

Pockets of liquid coalesce leading to the gel shrinking
As the vitreous contracts, vitreoretina adhesions are weakened, leading to vitreous pulling away from retina

26
Q

What percentage of people over 65years have PVD

A

About 70%

27
Q

What other comditions increases risk of PVD esp in younger age

A

High myopia
Traumatic injuries eg retinal tear, vitreous haemorrhage

28
Q

What is the cause of most physiologic floaters

A

Small amounts of debris present in the vitreous, from the embryonic hyaloid vascular system

29
Q

Causes of other floaters

A

Collagen fibrils clumping together
Vitreous hemorrhage
Release of debris from infectious conditions eg uveitis

30
Q

What is the function of vitreous

A

Coordinating eye growth
Protects eye during mechanical trauma
Maintains eye shape
Refractive properties

31
Q

Common complications of PVD

A

Retinal tears
Macula hole
Retinal detachment

32
Q

What are some causes of the perception of flashing lights

A

PVD
Retinal traction/tears
Retinal detachment

33
Q

What is the most abundant macromolecule in the vitreous

A

Hyaluronic acid

Eye And Visual Pathways (8 decks)

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