The prime functions of the uveal tract as a unit are:
- Nutrition and gas exchange: uveal vessels directly perfuse the ciliary body and iris, to support their metabolic needs, and indirectly supply diffusible nutrients to the outer retina, sclera, and lens, which lack any intrinsic blood supply. (The cornea has no adjacent blood vessels and is oxygenated by direct gas exchange with the environment.)
- Light absorption: the uvea improves the contrast of the retinal image by reducing reflected light within the eye (analogous to the black paint inside a camera), and also absorbs outside light transmitted through the sclera, which is not fully opaque.
In addition some uveal regions have special functions of great importance, including secretion of the aqueous humour by the ciliary processes, control of accommodation (focus) by the ciliary body, and optimisation of retinal illumination by the iris's control over the pupil. Many of these functions are under the control of the autonomic nervous system.