Lecture 30- Vitreous Part I (Combined)

An extended extracellular matrix situated between the lens and retina, the largest structure within the eye.

Vitreous

Strongest vitreal attachment

Located at the ora serrata, known as the vitreous base.

The space behind the lens where the lens and vitreous are juxtaposed but not joined.

Retrolental space (of Berger)

A major component of the vitreous that maintains the wide spacing between collagen fibrils.

Hyaluronic acid

98.5% to 99.7% water with 0.3% to 1.5% solid materials.

Vitreous composition

The type of vitreous that develops during embryonic life and regresses after birth.

Primary vitreous

The outermost zone of the vitreous composed of tightly packed collagen fibrils.

Vitreous cortex

Also known as Cloquet's canal, a channel located in the center of the vitreous body.

Hyaloid channel

The most common age-related event in which the vitreal cortex separates from the ILM of the retina.

Posterior vitreous detachment

True or False: Fibroblasts make hyaluronic acid.

False; fibroblasts do not synthesize hyaluronic acid.

Occurs when the vitreous pulls away from the retina but the attachment to the ILM is too tight.

Vitreoretinal traction

The indentation in the vitreous where the lens sits.

Patellar fossa

A condition characterized by bleeding into the vitreous cavity.

Vitreous hemorrhage

A condition where small, white, spherical opacities form in the vitreous.

Asteroid hyalosis

Collagen types in vitreous

Type II, Type IX, Type V/XI, and Type IV

What 2 things allow for minimal light scatter?

Low particle concentration and high water content

Acts to stabilize retinal metabolism and potassium homeostasis.

Metabolic buffer function of vitreous

Colloquially called a common result of condensation, visible as a 'floater'.

Vitreous bubble

Functions of the vitreous

Mechanical support, protection, light transmission, and nutrient storage.

Occurs when the vitreous begins to pull away but remains attached to the retina.

Visual distortion due to vitreoretinal adhesion

Vitreous gel and liquid ratio by age 10

Vitreous is about 50% gel and 50% liquid

Microstructural components comprising the majority of the solid materials in the vitreous.

Collagen fibrils

The vitreous metabolizes oxygen to absorb UV light, protecting the lens and retina.

Retinal metabolism protection

The embryonic structure that regresses to form the hyaloid channel.

Hyaloid artery

Created by an interval between the posterior lens and the anterior vitreous.

Berger's space

Begins during the 20th week of gestation.

Secondary vitreous development

A disruption in the HA-collagen complex, leading to visible fibrous structures.

Vitreous condensation

The area of strongest attachment located at the ora serrata.

Vitreous base

Cells in the vitreous that synthesize hyaluronic acid, glycoproteins, and collagen fibrils.

Hyalocytes

Involved in ocular structure maintenance, light transmission, and metabolism.

Vitreous structure roles

The vitreous body plays significant roles in metabolic functions affecting eye health.

Ocular health impact

Mittendorf's dot is a remnant of the primary vitreous, observable on biomicroscopy.

Crystalline lens remnant

What is the anatomical structure and composition of the vitreous body?

The vitreous is an extended extracellular matrix situated between the lens and retina, comprising 98.5% to 99.7% water and various collagen types.

What is the volume and axial length of the vitreous body?

The vitreous body has a volume of approximately 4.0 mL and an axial length of 16.5 mm.

What is the primary function of the vitreous body?

The primary functions include mechanical support, protection, light transmission, and supporting eye development.

How does the vitreous body maintain media transparency?

The vitreous maintains media transparency by its high water content and low concentration of particles, resulting in minimal light scatter.

What is the role of hyaluronic acid in the vitreous body?

Hyaluronic acid maintains spacing between collagen fibrils, stabilizes the gel structure, and contributes to the viscoelastic properties of the vitreous.

What are the main components of the vitreous?

The vitreous is primarily composed of water, collagen, hyaluronic acid, and vitreal cells (like hyalocytes and fibroblasts).

What are the vitreal attachments and their strengths?

Strongest attachments include vitreous base at the ora serrata, followed by posterior lens, optic disc, macula, and retinal vessels.

How does the vitreous body protect the internal ocular structures?

The viscoelastic property of the vitreous acts as a shock absorber, protecting against damage from physical activity or injuries.

What does the vitreous chamber consist of?

The vitreous chamber is filled with the gel-like vitreous body and occupies about 80% of the eye's volume.

What changes occur in the vitreous during aging?

During aging, the vitreous body tends to detach from the retina, which usually occurs innocuously.

What is Cloquet’s canal?

Cloquet's canal (or hyaloid channel) is the innermost part of the vitreous body, a remnant of the hyaloid artery system.

What types of collagen are predominantly found in the vitreous?

Type II collagen (60-75%) and Type IX collagen (15-25%) are the predominant collagen types in the vitreous.

What is the effect of ocular metabolic function?

It regulates and distributes oxygen, provides nutrient storage, and acts as a metabolic buffer for the retina.

What is the significance of the vitreous base?

The vitreous base is the strongest attachment point located at the ora serrata, providing crucial support to the vitreous.

What is the role of vitreal cells like hyalocytes?

Hyalocytes synthesize hyaluronic acid, glycoproteins, and collagen fibrils, contributing to the composition of the vitreous.

What happens to the vitreous body during vitreal detachment?

During vitreal detachment, the vitreous might separate from the retina, potentially leading to symptoms like flashes or floaters.

What is the structure of the vitreous cortex?

The vitreous cortex is the outermost layer composed of tightly packed collagen fibrils about 100 μm wide.

Describe the intermediate zone of the vitreous body.

The intermediate zone consists of fine continuous fibers running anterior to posterior, forming membrane-like condensations.

What is the importance of nutrient transport in the vitreous?

The vitreous acts as a repository for essential nutrients and facilitates the transport of metabolic substances within the eye.

How does the vitreous body transmit light?

The vitreous transmits and refracts light with less than 10% scatter, thanks to its low particle concentration and high water content.

What is the connection between the vitreous body and eye growth?

The vitreous modulates eye growth by helping maintain the eye's shape during development.

Why is aging related to vitreous metabolic abnormalities?

Aging and other factors, like refractive conditions, can disrupt the metabolic balance and function of the vitreous.

What protective role does the vitreous play regarding lens oxidation?

The vitreous prevents lens oxidation by blocking oxygen diffusion from the retina.

What is the functionality of retrolental space in the vitreous?

The retrolental space is an area behind the lens where the lens and vitreous meet but are not joined—allowing flexibility.

What happens to collagen fibril density in the vitreous?

Collagen fibril network density varies, being highest at the vitreous base and lower in the hyaloid channel.

How does the composition of the vitreous relate to ocular health?

The composition, including collagen and hyaluronic acid, is crucial for maintaining viscosity, gel structure, and overall eye health.

What are some visual symptoms associated with vitreous detachment?

Symptoms can include flashes of light or floating spots in the vision as the vitreous separates from the retina.

How do hyalocytes differ from fibroblasts in the vitreous?

Hyalocytes are primarily involved in synthesizing gel components, while fibroblasts, comprising less than 10%, mainly produce collagen.

What is the physiological significance of the vitreous body's high water content?

The high water content allows for maximum light transmission and maintains the gel-like properties essential for ocular structure.

What metabolic role does the vitreous body play in oxidative stress?

The vitreous regulates oxygen metabolism and protects the lens and retina from oxidative stress by converting oxygen to ascorbate.