pigmented middle of the three concentric layers that make up an
part; Eye layer; Iris's place; Optic layer; Pigmented peeper
part; Ophthalmologist's concern; The eyes have it; Part of the
eye; Colored part of the eye
4 times a year
Laser Eye Surgery
suppose that the eye with all its inimitable contrivances for
adjusting the focus to different distances, for admitting
different amounts of light, and for the correction of spherical
and chromatic aberration, could have been formed by natural
selection, seems, I freely confess, absurd in the highest
Darwin, The Origin of Species
uvea (Lat. uva, grape), also called the uveal layer, uveal coat,
uveal tract, or vascular tunic, is the pigmented middle of the
three concentric layers that make up an eye. The name is possibly
a reference to its reddish-blue or almost black colour, wrinkled
appearance and grape-like size and shape when stripped intact
from a cadaveric eye. Its use as a technical term in anatomy and
ophthalmology is relatively modern.
section of the eyeball. The constituents of the uvea follow: iris
labeled at top, ciliary body labeled at upper right, and choroid
labeled at center right.
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,
cornea & lens, which lack any intrinsic blood supply.
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.
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.
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