Final answer:
The gel-like substance that prevents the eye from collapsing is called the vitreous humor, a viscous fluid that fills the posterior cavity of the eye.
Step-by-step explanation:
The gel-like stuff that keeps the eye from collapsing and is located on the posterior side of the eye is known as the vitreous humor. This viscous fluid fills the posterior cavity of the eye, which extends from the lens to the retina, supporting the shape of the eyeball and providing a pathway for light to reach the photoreceptive cells of the retina. The vitreous humor helps maintain the eye's structural integrity and ensures that the retina remains adequately positioned for optimal function.