The vitreous body is a transparent, gel-like substance that fills the vitreous cavity, which makes up approximately 80% of the volume of the eyeball and occupies the space between the posterior surface of the lens and the retina. It consists of approximately 98-99% of water, with the remainder made up of collagen fibres (mainly type II collagen), hyaluronic acid, proteins (vitrosin, opticin), electrolytes and a few cells called hyalocytes. The collagen fibres form a three-dimensional structural network that, when young, is tightly bound to hyaluronic acid molecules, giving the vitreous body a uniform, gel-like consistency and ensuring its optical transparency due to the precise ordering of the fibres minimising light scattering. The vitreous body has a number of important physiological functions, including mechanically supporting the shape of the eyeball, cushioning shock and trauma, maintaining the retina in its correct position adjacent to the pigment epithelium, and providing a metabolic pathway for the transport of nutrients and metabolic products between the aqueous fluid and the retina.
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