Physiology of accommodation and role of the vitreous body

Abstract

The eye is a three-chambered system, consisting of the anterior chamber, posterior chamber, and vitreous compartment. The anterior and posterior chambers are separated by the iris and filled with aqueous fluid produced by the ciliary epithelium and flowing from the posterior to the anterior chamber through the pupil. Fluid is constantly replenished and “turned over” in both the aqueous and the vitreous. The fluid “relief valve” is primarily movement of the aqueous from the eye via the trabecular meshwork and Schlemm’s canal, but also is transported from the eye via a secondary uveoscleral outflow route [1–3] involving the ciliary body, choroid, sclera, and episcleral tissues. The anterior and posterior chambers are normally in communication through the pupil and hence in pressure equilibrium. The vitreous is normally also in pressure equilibrium with the aqueous. Remarkably, this pressure equilibrium is maintained during growth and development when there are significant changes in anatomy.