Vitreous Substitutes: The Present and the Future

Table 1

Biochemical composition of the vitreous.

Subgroups	Molecule	Action
Protein	Albumin (40%)
	Iron binding protein (30%) like transferrin	Protective effect to reduce iron toxicity
	Collagens	Structure of the vitreous
	Type II (60–70%)
	Type IX (25%)
	Type V/IX (10–25%)
	Type IV (<10%)
Glycosaminoglycan	Hyaluronic acid (66–115 microgram/mL concentration)	Determine the vitreous body viscosity
	Chondroitin sulfate	Major component of extracellular matrix
	Versican
	Type IX collagen
	Heparan sulfate	It maintains adequate spacing between the collagen fibrils
Metabolites	Glucose	To support the enzymatic activity
	Lactic acid
	Ascorbic acid	Neovascularization inhibitor Increase proliferation of hyalocytes Potent antioxidant
	Amino acids	Metabolic cells maintenance
	Fatty acids unsaturated (50–55%)	Metabolic cells maintenance
	Prostaglandins (100 picogram/mL)	Cells regulation
	PGE2	Cells regulation
	PGF2alpha	Cells regulation
	Prostacyclin	Cells regulation
	Thromboxane	Cells regulation
Cells	Hyalocytes	Vitreous matrix creation and maintenance
	Fibrocytes/fibroblasts	Vitreous matrix creation and maintenance
	Macrophages	Cells and matrix regulation and degradation
	Enzymes and metabolic activity: ACE	Cells regulation