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The middle coat of the eye is composed of three pigmented structures:
The iris if the pigmented diaphragm which lies upon the lens and separates the anterior chamber of the eye from the posterior chamber. The sphincter pupillae (parasympathetic innervation via the IIIrd nerve) and the dilator pupillae (cervical sympathetic innervation) control the size of the pupil.
The ciliary body has two roles:
The choroid is highly vascular and, together with the central retinal artery, provides nutrients to the retina.
The major disorders of the middle coat of the eye may be classified as below: