Vitreous

Question 1

what is the size of Vitreous chamber in newborns and in adults?

Answer 1

Newborn ≈10.5mm

Adult ≈16.5mm

Question 2

The vitreous is what percent of the total volume of the eye?

Answer 2

The vitreous is ≈80% of the volume of the eye (largest structure)

Question 3

What is the vitreous composed of?

Answer 3

98 % water and collagen and glycosaminoglycans (GAGs) form the vitreous into a viscoelastic gel

Question 4

What happens to the gel content of the vitreous with age?

Answer 4

Gel content decreases with age

Question 5

What types of collagen fibers are found in the Vitreous?

Answer 5

75% type II collagen and 10% type V/XI collagen

Question 6

What is Cloquet’s canal?

Answer 6

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

Question 7

What is considered tertiary vitreous?

Answer 7

The Zonules

Question 8

Vitreous is made up of what parts?

Answer 8

Cortex: outermost part of the vitreous
Base: three dimensional zone extending from 2mm anterior to 3mm posterior to the ora serrata; it is several mm thick
Collagen fibrils are densely packed here

Question 9

T/F: Outer part of the cortex, includes the retina internal limiting membrane (ILM) and anchoring fibrils of the body

Answer 9

True.

Question 10

How thick is the ILM (internal limiting membrane) ?

Answer 10

1-3 microns thick

Question 11

The Vitreous cortex is firmly attached to the ILM in which locations?

Answer 11

1. At the vitreous base
2. Around the optic disc (Weiss ring)
3. At the vessels
4. In the area surrounding the foveola

Question 12

T/F: Gel structures of the vitreous acts as barrier against the movement of solutes

Answer 12

True

Question 13

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

Answer 13

Fluorescein

Question 14

What causes bulk flow in the vitreous?

Answer 14

Bulk flow result of a pressure gradient from the anterior to posterior pole of the eye
*Large, high molecular weight substances move due to this gradient

Question 15

T/F Bulk flow plays an important role in distribution of low molecular weight substances in the vitreous

Answer 15

False.

Question 16

What is synchysis?

Answer 16

Liquefacation of the gel structure of the vitreous caused by aging

Question 17

Why does vitreous collagen molecular weight increases with age?

Answer 17

due to;

secondary to new covalent cross-links

Maillard Rxn- insoluble proteins produced by a covalent bond between an amino group and glucose

Question 18

What is Posterior Vitreous Detachment (PVD)?

Answer 18

when the central degeneration is large and causes a collapse -> the cortex sinks to the center of the vitreous body
*considered a normal aging phenomena

Question 19

What is the first tear in rhegamatogenous retinal detachment?

Answer 19

Retinal tear (occurs when there is a strong attachement b/n posterior cortex and the ILM)

Question 20

T/F: The vitreous can act as a metabolic buffer and a reservoir for metabolism of the ciliary body and the retina

Answer 20

True