What fills the anterior segment of the eye?

The anterior segment of the eye is primarily filled with aqueous humor, a transparent fluid that is produced by the ciliary body. This fluid circulates through the anterior chamber, which is located between the cornea and the iris, and it provides several important functions. Aqueous humor helps maintain intraocular pressure, supplies nutrients to the avascular structures of the eye such as the lens and cornea, and removes metabolic waste.

In contrast, the vitreous humor, while also a fluid in the eye, is located in the posterior segment, filling the larger space behind the lens and extending to the retina. Blood plasma and corneal fluid are not components typically associated with the filling of the anterior segment. Blood plasma is part of the circulatory system, and corneal fluid is not a standard term used in ocular anatomy. Thus, aqueous humor stands out as the essential fluid filling the anterior segment of the eye.