Ocular: Vitreous

Question 1

What is the vitreous body?

Answer 1

Clear gel that occupies the clear compartment of the eye

Question 2

What is the largest structure of the eye?

Answer 2

The vitreous body

Question 3

What is the vitreous located between?

Answer 3

Crystalline lens and the retina

Question 4

What volume and percentage of the eye is the vitreous?

Answer 4

4mL, 80% volume

Question 5

What is the function of the vitreous?

Answer 5

-storage area for metabolites for retina and lens
-medium for movement of metabolites
-acts as a UV filter by decreasing light to protect retina
-shock absorber

Question 6

Anterior boundaries of the vitreous:

Answer 6

-posterior surface of the lens
-retrozonular portion of the posterior chamber

Question 7

What makes up the posterior boundaries of the vitreous?

Answer 7

The pars plana, retina, and optic nerve

Question 8

What is primary vitreous?

Answer 8

Vitreous produced in the 3rd-4th week of gestation

Question 9

What releases VEGF? What does that induce?

Answer 9

-lens releases VEGF
-induces vasculogenesis which causes the hyaloid vasculature to fill the optic cup

Question 10

What is secondary vitreous?

Answer 10

Vitreous formed in the 6th week of gestation where the vitreous cavity increases in size

Question 11

What is the cloquets canal?

Answer 11

-hyaloid artery disappears creating a tube of primary vitreous surrounded by secondary vitreous —> forming cloquets canal

Question 12

What is tertiary vitreous in the adult? What forms it?

Answer 12

-tertiary vitreous is the zonules of the lens
-secreted by the NPCE

Question 13

Where is the vitreous base located?

Answer 13

At the ora serrata

Question 14

How broad is the vitreous base?

Answer 14

5mm

Question 15

What is the vitreous base connected to?

Answer 15

The NPCE of ciliary body and the ILM of the peripheral retina

Question 16

How is collagen oriented in relation to the pars plana?

Answer 16

Orthogonal

Question 17

Where is the strongest attachment of vitreous?

Answer 17

The vitreous base

Question 18

Does the vitreous base weaken with age?

Answer 18

NO

Question 19

What are hyalocytes?

Answer 19

Cells that synthesize hyaluronic acid, proteins, and act as phagocyte —> *most numerous at vitreous base

Question 20

What do fibroblasts do?

Answer 20

Synthesize collagen fibrils in vitreous

Question 21

What is the patellar fossa?

Answer 21

An impression the lens makes on the anterior vitreous

Question 22

What are all the structures that interface with the vitreous body?

Answer 22

-lens capsule
-NPCE of ciliary body
-ILM of retina

Question 23

If a structure is in contact with the vitreous base, what is it?

Answer 23

A basement membrane

Question 24

What is Weiger’s ligament?

Answer 24

-A ligament located between the posterior capsule of the lens and anterior vitreous cortex
-firm annular attachment

Question 25

Does Weiger’s ligament weaken with age?

Answer 25

YES

Question 26

What is the space of Berger?

Answer 26

A potential space within the center of Weiger’s ligament because the vitreous and lens are juxtaposed rather than joined

Question 27

What is the cloquet’s canal?

Answer 27

a 1-2mm wide channel running through the center of the vitreous body what contained the hyaloid vasculature during embryonic development

Question 28

What is the cloquets canal DEVOID of?

Answer 28

Collagen filaments

Question 29

Where does the cloquets canal extend to/from?

Answer 29

Extends anteroposteriorly from the retrolental space behind the lens to a funnel-shaped area over the optic nerve head

Question 30

What is a Mitterndorf’s Dot?

Answer 30

A small circular opacity on the posterior capsule of the lens that has an anterior attachment

Question 31

What are Bergmeister’s papillae?

Answer 31

A small tuft if fibrous tissue that remains from the hyaloid vasculature at the optic disc with a posterior attachment

Question 32

What is a peripapillary adhesion?

Answer 32

When the vitreous is still attached around the edge of the optic disc -> is a medium attachment that will weaken w age

Question 33

What are macular and peripheral attachments of vitreous?

Answer 33

A weak vitreous attachment that can attach 3-5mm below the vitreous base and can attach to retina blood vessels

Question 34

What are the two zones of the vitreous body?

Answer 34

cortical zone and medullary zone

Question 35

Describe the cortical zone of the vitreous body:

Answer 35

-peripheral -encases medullary zone -condensed fibrillation tissue -2% vitreous volume * -metabolic center of vitreous* -hyalocytes and some fibrocytes

Question 36

Describe the medullary zone of the vitreous:

Answer 36

-center 98% of volume* -cell-free mixture of collagen adn hyaluronic acid -gel or liquid state

Question 37

Anterior cortex of the vitreous location:

Answer 37

Extends anterior to vitreous base and is adjacent to ciliary body, posterior chamber, and lens

Question 38

Posterior cortex of the vitreous location:

Answer 38

Extend posterior to vitreous base in contact with the ILM of retina

Question 39

What happens in a posterior vitreous detachment?

Answer 39

-vitreous gel separates from retina -vitreous synthesis is most common cause of

Question 40

Complications of posterior vitreous detachment:

Answer 40

-vitreous hemmorage -retinal detachment -epiretinal membrane -macular hole

Question 41

What can you see where the PVD pulls away from the optic disc?

Answer 41

Weiss ring

Question 42

How and where can a PVD induce traction on the retina?

Answer 42

If there is a strong attachment between the vitreous and the ILM, especially seen in foveal region

Question 43

What has been argued to be primary pathogenic event in idiopathic macular hole formation

Answer 43

Perifoveal vitreous detachment

Question 44

What is the vitreoretinal interface?

Answer 44

The outermost portion of the posterior cortex that contains anchoring fibers that merge with the ILM of the retina

Question 45

How thick is the ILM of the retina? What is it the basal lamina made up of?

Answer 45

1-3 microns thick, foot processes of the muller cells

Question 46

Where do the anchoring fibrils of the vitreoretinal interface pass through? What can this cause?

Answer 46

-pass through the ILM of the retina to surround the retinal vessels in the nerve fiber layer -may cause hemorrhages that occur with vitreoretinal traction

Question 47

What is the main collagen type in vitreous?

Answer 47

Type II

Question 48

What is the percentage of water in vitreous?

Answer 48

98.5-99.7%

Question 49

What is hyaluronic acid?

Answer 49

A non-sulfated GAG

Question 50

What are the vitreal cells?

Answer 50

Hyalocytes and fibroblasta

Question 51

How much glucose is in vitreous?

Answer 51

30-70mg/100mL H₂O

Question 52

Is there a high or low [ ] of vitamin C in vitreous?

Answer 52

High

Question 53

What are the molecules in vitreous?

Answer 53

Na+, K+, Cl-

Question 54

What is the relationship between collagen fibers and HA?

Answer 54

Collagen fibers aggregate into packed parallel bundles and HA molecules fill the spaces between the collagen and form a channels of liquid vitreous

Question 55

Why are collagen fibers and HA important for vitreous?

Answer 55

The viscoelastic properties of vitreous only occur when both materials are combined

Question 56

What do hyalocytes do?

Answer 56

-synthesize glycoproteins for the collagen fibrils -synthesize hyaluronic acid

Question 57

What do fibroblasts do?

Answer 57

Synthesize the collagen fibrils

Question 58

What is the effect of aging on the vitreous?

Answer 58

Disintegration of the gel structure

Question 59

Four major functions of the vitreous body:

Answer 59

1. Support for retina 2. Diffusion barrier between anterior and post segments 3. Metabolic buffer 4. Transparency

Question 60

Describe the support function of vitreous:

Answer 60

-prevent retinal detachment -reduce mechanical deformation -support lens trauma -decrease transmission of ligth at 300-350nm

Question 61

Describe the diffusion barrier function of the vitreous body:

Answer 61

-slow diffusion across the vitreous -limited bulk flow -present topical substances from reaching retina -prevent substances in blood stream from reaching vitreous center

Question 62

Describe the metabolic buffer function of vitreous:

Answer 62

-reservoir for ciliary body and retinal metabolism -movement of water soluble substances into vitreous for diffusion -resoivoir of potassium for retinal metabolism -reservoir for vitamin C

Question 63

Describe the transparency function of vitreous:

Answer 63

-low [ ] oof structural macromolecules (<0.02%) -low [ ] soluble proteins -specific collagen/HA formation -blood/vitreous barrier

Question 64

Describe vitreous syneresis and floaters:

Answer 64

When the gel structure of vitreous becomes more liquified with age and water starts to collect into pockets (lacunae) that cause vitreous gel to break down and cause aggregation of collagen fibrils —> floaters