1. The transparent, jellylike material that fills the eyeball between the retina and the lens.
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.