Flashcards in Vitreous Deck (37)
How much percentage wise does the vitreous take over
80% of the volume of the eye and is the largest single structure of the eye
How many mm is the vitreous chamber in a newborn? What about an adult?
Newborn: 10.5 mm
Adult: 16.5 mm
How much water is in the vitreous?
What are the non aqueous components of the vitreous
Collagen and GAGs form the vitreous into a viscoelastic gel
T/F gel content decreases with age
what types of collagen are in the vitreous?
Type II collagen: 75%
Type V and VI: 10%
What are some difficulties that arise when investigating the vitreous
1. Vitreous is supposed to be invisible
2. Previous techniques are combined with artifacts, so its hard to make interpretations on the true in vivo situation
What is the embryology of the vitreous
1. The optic cup is occupied by the lens vesicle
2. The cup grows and the space is filled by fibrillar material secreted by embryonic retina
3. The hyaloid artery penetrates and more fibrillar material from blood vessel cells fills the space
4. the mass in the end is the primary vitreous
How does the second vitreous form
1. The size of the vitreous cavity increases and the hyaloid vascular system regresses
2. Main hyaloid artery maintains for a period of time then disappears and leaves the cloquet's canal
What is Cloquet's canal
A tube of primary vitreous surrounded by secondary vitreous running from the retrolental space to the optic nerve
What refers to tertiary vitreous
Zonules of the lens, which are the suspensor fibrils that are developed from the fibrillary material
What is the mature vitreous body
A transparent gel that occupies the vitreous cavity. It has a spherical appearance, except for the anterior part, which is concave
What is the outermost part of the vitreous
Cortex; divided into an anterior and posterior cortex
What does the base consist of
Base; 3 dimensional zone extending from 2 mm anterior to 3 mm posterior to the ora serrata. This is where the collagen fibrils are densely packed
What makes up the outer part of the cortex?
The Vitreoretinal interface, which includes the retina and ILM (internal limiting membrane) and anchoring fibrils of the body
What type of collagen makes up the ILM
type IV collagen and proteglycans; considered the basal lamina of the Mueller cells
Where are the various locations that the vitreous cortex is firmly attached to
1. At the vitreous base
2. Around the optic disc (Weiss ring)
3. At the vessels
4. In the area surrounding the foveola
What do OCT findings show
That in 60% patients there are preretinal strands which are the first signs/precursors to detachment. Patient has no idea. This is asymptomatic
If foveal anatomy is not the same what happens with the patient
-but patient sees 20/20. VA does not got down!
Ascorbic is greater in the vitreous than in the blood.
What is the vitreous' primary job
To act as a buffer
What is the same thing as Glycasaminoglycans
Hylaranic acid/ hyalourin which there is a lot in vitreous
what does the gel structure act as a barrier against
The movement of solutes by diffusion or bulk flow
When does bulk flow happen
happens as a result of possible pressure gradient from the anterior part of the eye toward the posterior pole of the eye. Only high, large molecular weight substances move due to this gradient
What is the main change in aging effects in regards to the vitreous
Main change: Liquification of the gel structure aka SYNCHYSIS, most notable in the center of the vitreous. The gel structure is dissolved and replaced with aqueous lacunae
What are other aging effects in regards to the vitreous
Vitreous collagen molecular weight increases with age because of the formation of new covalent cross links between the peptide chains.
What is the Mailard reaction
Proteins are cross linked because of this - insoluble proteins produced by a covalent bond between an amino group and glucose
What are the 4 main aspects of the vitreous
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
How does the vitreous support the retina?
Helps prevent a large retinal detachment and absorbs external forces to protect globe deformation