2. The transparent gelatinous substance filling the eyeball behind the crystalline lens.
The vitreous humor contains very few cells; mostly phagocytes which remove unwanted cellular debris in the visual field), no blood vessels, and 99% of its volume is water with salts, sugars, and a network of collagen fibers with hyaluronic acid accounting for the rest; however, the vitreous has a viscosity two to four times that of pure water, giving it a gelatinous consistency.
Hyaluronic acid is a complex viscous substance that lubricates joints in the body and is present in connective tissue. It also plays a role in the healing of wounds.