Vitreous Anatomy

Intro

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Structure & Function

The vitreous humour is a viscous, "gel-like" fluid located within the posterior segment of the eye. It functions to:

• Maintain the eye's shape

• Store and distribute oxygen and nutrients to the eye

It encompasses a majority (approx. 80%) of the eye’s volume, with bordering the posterior lens capsule, following alongside the inner retina and extending to the macula. It is filled with a homogenous, highly transparent extracellular matrix (ECM) known as the vitreous humour. Although primarily comprised of water (98%) and minimal macromolecules (2%), its consistency is gelatinous and quite viscous at birth. This is attributed to the delicate interactions between the remaining macromolecular components (2%).

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Regions of the Vitreous

The vitreous is classified into three regions:  

• The vitreous body has the lowest concentration of collagen and HA. Collagen fibrils are organized

• The vitreous base surrounds the ora serrata. It is densely packed with collagen fibers that adhere firmly to the inner limiting membrane (ILM) of the retina; thus is the strongest site of vitreoretinal adhesion. {de Smet, 2013 #272}

• The vitreous cortex is a thin layer of densely packed collagen that surrounds the vitreous body circumferentially. It is further classified as anterior vitreous cortex, which borders the posterior lens capsule, and the posterior vitreous cortex (PVC), which borders the ILM.

The vitreous is predominantly acellular, apart from a small layer of hyalocytes located within the outer PVC, about 50 μm from the inner retina. Hyalocytes synthesize non-cellular vitreous components including collagen and hyaluronic acid. {de Smet, 2013 #272} They also play a significant part in vitreomacular pathology and will be further discussed below.

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References

{Phillips, 2022 #300}