IOA2 Exam 2 - Vitreous Humor

When does the primary vitreous develop?

at the end of the 3rd embryonic week

The primary vitreous is located behind the _______.

lens vesicle

What forms the primary vitreous?

Mesoderm migrating between the optic cup and lens vesicle.

The primary vitreous primarily consists of the:

hyaloid vasculature

Hyaloid artery

An artery that supplies nutrients to the tissue behind the lens and the lens

The secondary vitreous starts to develop by:

the ninth week

What is the secondary vitreous synthesized by?

Primary vitreal cells and retinal glial cells (neuroectoderm origin)

What does the secondary vitreous become?

Mature vitreous

The mature vitreous is mostly ________ and _______.

acellular and fibrous

The secondary vitreous eventually fills the ______ and compacts the primary vitreous.

globe

When does the tertiary vitreous develop?

at 6 months embryonically

What does the tertiary vitreous form?

zonular fibers

The fibrous structure of the secondary vitreous condenses and forms the ______.

zonules

What do the zonules merge with during vitreous development?

Lens capsule and the BM of the ciliary body

What happens to the hyaloid vasculature before birth?

It dissolves through an autolytic process (the vasculature dissolves itself)

The canal that is left after the primary vitreous dissolves is called the

Canal of Cloquet (aka hyaloid canal)

How does the Canal of Cloquet change over time?

At birth, it runs straight; with aging, it becomes serpentine

With liquefaction, the canal of Cloquet becomes more

mobile (ascension phenomenon)

The vitreous chamber is filled with

gel-like vitreous body

The vitreous makes up _____% of the entire volume of the eye.

80%

Volume of the vitreous chamber vs. size of the eye

4 ml (vitreous chamber)

5 ml (size of eye)

Shape of the vitreous humor

Spherical shape except for the center of the anterior surface

Indentation located in the center of the anterior surface of the vitreous chamber, where the lens sits

Patellar fossa

What are the main components of the vitreous chamber (6)?

1) 98.5-99.7% water

2) Collagen

3) GAG substance

4) Hyalocites

5) Vitamin C

6) Amino acids

Type of collagen fibers in the vitreous chamber

Type II collagen fibers

Main type of GAG in the vitreous chamber

Hyaluronic acid

What are hyalocites and where are they located in the vitreous chamber?

vitreous cells located at the cortex near the vitreal surface

Is the concentration of Vitamin C in the vitreous humor higher or lower than in blood plasma?

Higher

Is the concentration of Amino Acids in the vitreous humor higher or lower than in blood plasma?

Lower

In early life, the vitreous chamber is

gel like (jelly)

What happens to the vitreous as we age (70-80 years)?

Becomes more liquid in the center, forming:

1) pockets of fluid

2) aggregation of collagen fibrils - floaters

5 main attachments to the vitreous (retina and lens)

1) Vitreous base (strongest)

2) Posterior lens

3) Optic disc

4) Macula (annular ring)

5) Retinal vessels

Which vitreous attachment is the strongest and most extensive?

Vitreous base

Where is the vitreous base located?

It extends 1.5 - 2mm anterior to the ora serrata

What is the shape of the vitreous attachment at the macula?

annular ring (ring shaped)

How does the vitreous attach to the retinal vessels?

Fine strands extend through the internal limiting membrane to branch and surround the larger retinal vessels

Which attachments are most likely to cause a retinal tear?

The tightest attachments

Name the 4 vitreous regions

1) Anterior hyaloid

2) Vitreous cortex

3) Intermediate zone

4) Cloquet's Canal

The anterior hyaloid contains the

1) Weiger's ligament (retrolental ligament)

2) Berger's Space

Weiger's ligament

Ring-shaped attachment at the posterior lens capsule in the anterior hyaloid region

Berger's Space

Space between the ligament and the lens

Is considered the outer region of the vitreous

Vitreous cortex

The Vitreous Cortex contains (4):

-Collagen fibrils

-Cells

-Proteins

-Muco-polysaacharides

What are the subdivisions of the vitreous cortex?

1) Anterior vitreous cortex

2) Posterior vitreous cortex

Anterior Vitreous Cortex

Extends to the ora serrata and has a hyaloid surface (hyalocites)

Posterior Vitreous Cortex

Contains transvitreal channels that appear as holes

Types of transvitreal channels (holes) that are in the posterior vitreous cortex

1) Peripapillary hole

2) Premacular hole

3) Prevascular fissures

What is found in the intermediate zone of the vitreous?

Fine, unbranched fibers running antero-posteriorly

Cloquet's Canal is aka

Hyaloid channel

What is Cloquet's Canal

An S-shaped normal remnant of primary vitreous (at the center) that represents the site of the former embryological hyaloid artery

Cloquet's Canal terminates at the ________.

area of Martegiani

Area of Martegiani

Funnel-shaped space at the optic nerve head

Functions of the Vitreous

1) Transparent medium of passage of light

2) UV filter

3) Cushion to the globe

4) Shock absorber

5) Storage of nutrients

Refractive index of the vitreous

1.33

The vitreous acts as a UV filter by decreasing transmission of light at

300-350nm

The vitreous acts as a cushion to the _______.

globe (especially retina and lens)

The vitreous absorbs:

vibrations and external forces during trauma and eye movements

The vitreous acts as a storage area of nutrients for the _______ and _______.

retina and lens

Bleeding into the vitreous cavity

Vitreous hemorrhage

Causes of Vitreous Hemorrhage (2)

-Neovascularization

-Rupture of normal vessels

Causes of vitreous hemorrhage due to Neovascularization

-Proliferative diabetic retinopathy

-Central retinal vein occlusion (CRVO)

Causes of vitreous hemorrhage due to Rupture of normal vessels

-Retinal tear

-Trauma

-Posterior vitreous detachment

-Retinal detachment

Separation of the posterior vitreous cortex from the retina

Vitreous detachment

Causes of Vitreous Detachment (2)

-Trauma

-Posterior vitreous detachment

Posterior vitreous detachment usually results from:

normal, age-related changes in the vitreous gel

What is Weiss Ring?

A sign of posterior vitreous detachment

What population does Asteroid Hyalosis present in and what what composition is the vitreous made of?

Elderly population, calcium deposits

Is Asteroid Hyalosis typically unilateral or bilateral?

Unilateral

Describe the typical appearance of asteroid hyalosis in the vitreous.

Spherical, white opacities that move with the vitreous

What population does Synchysis Scintillans present in and what what composition is the vitreous made of?

Young population, cholesterol crystals

Is Synchysis Scintillans typically unilateral or bilateral?

Bilateral

Describe the typical appearance of synchysis scintillans in the vitreous.

Highly refractile, multicolored crystals that move freely and fall to the floor of the vitreous chamber