The ciliary body is a ring of tissue behind the iris that links the iris to the choroid. Its folded inner part (the ciliary processes) secretes aqueous humour, and its smooth muscle (the ciliary muscle) changes the shape of the lens through the zonular fibres. Its flat back part, the pars plana, ends at the ora serrata.
| Location | Between the iris and the choroid, behind the limbus |
|---|---|
| Parts |
|
| Nerve Supply | Short ciliary nerves (parasympathetic from the ciliary ganglion, CN III origin); Long ciliary nerves |
| Blood Supply | Long posterior ciliary arteries; Anterior ciliary arteries; Major arterial circle of the iris |
Produces aqueous humour, controls lens focusing for near vision and anchors the zonular fibres that hold the lens.
Contraction of the ciliary muscle relaxes the zonules so the lens rounds up for near focus (accommodation), which weakens with age as presbyopia. Glaucoma drugs such as beta blockers and carbonic anhydrase inhibitors reduce aqueous production by the ciliary epithelium. The pars plana is the safe entry site for intravitreal injections and vitrectomy because it has no retina.
Inflammation centred on the pars plana and vitreous base, causing floaters and blurred vision. It can be linked to multiple sclerosis or sarcoidosis.
Separation of the ciliary body from the scleral spur after blunt trauma. It allows aqueous to escape and can cause dangerously low eye pressure.
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