Gel-like fluids inside the eye help it maintain its shape, which plays an important role in overall eye health. These substances are called the vitreous humor and aqueous humor.

Vitreous is a transparent substance that is around 99 percent water. The remaining one percent is collagen and hyaluronic acid, which cause vitreous to have a gelatinous consistency. Along with maintaining the shape of the eye, the vitreous helps absorb shocks to the eye and keeps the retina properly connected to the back wall of the eye. Light passes through the vitreous on its way to the retina.

Vitreous in children has a consistency that resembles egg whites. As people age, it becomes more liquid. Thinning vitreous can cause the retina to separate from the back wall of the eye, often resulting in floaters — spots that appear to float in the field of vision. This separation is called posterior vitreous detachment and occurs in the majority of people by age 70. So long as no retinal tearing occurs, this condition usually resolves itself without treatment.

Aqueous is a thin, watery fluid located in the anterior and posterior chambers of the eye. The anterior chamber lies between the iris (colored part of the eye) and the inner surface of the cornea (the front of the eye). The posterior chamber is located behind the iris and in front of the lens. In addition to supporting the shape of this area, aqueous supplies nutrients and nourishment to parts of the eye that lack blood supply. It also removes waste.

Improper drainage of the aqueous humor can cause an increase in intraocular pressure (pressure inside the eye). This increase can result in loss of vision or contribute to the development of glaucoma. Issues with aqueous humor drainage can be treated surgically.