Disease of the middle coat of the eye

The middle coat of the eye is composed of three pigmented structures:

• iris }
• ciliary body } collectively referred to
• choroid ] as the uvea

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 production of aqueous humour
• accomodation - via the zonular fibres which attach to the lens

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:

• congenital
• traumatic
• uveal inflammation
• tumour of the uvea