The ciliary body is the continuation of the uveal layer of the eye and functions in the production of aqueous humour and the process of lens accommodation. 

Summary

• location: between the vitreous body and posterior chamber of the globe

• function: aqueous humour production and accommodation of the lens

• arterial supply: anterior ciliary arteries and long posterior ciliary arteries

• venous drainage: vorticose veins

• innervation: short ciliary nerves

• relations: vitreous cavity posteriorly, posterior chamber anteriorly, scleral layer externally, retinal layer internally  

Gross anatomy

The ciliary body is a continuation of the uveal tract, with the choroid lying posteriorly and iris anteriorly. The uveal tract lies between an outer scleral layer and inner retina layer of the eye ¹. It forms a flat ring and contains the ciliary process, ciliary muscles and ciliary vessels.

The ciliary processes are finger like protrusions of the ciliary body and attach to the lens via the zonula fibres (suspensory ligaments), allowing for the process of accommodation. The ciliary processes contain specialised vascular epithelium that secrete aqueous humour into the globe of the eye ¹.

The ciliary muscles consist of three differently orientated smooth muscle fibres. The outermost longitudinal fibres attach the ciliary body to the scleral spur and function to open the trabecular network and Schlemm’s canal ². The innermost circular fibres relax the zonular fibres when contracted, allowing for an increase in lens axial diameter and convexity. Radial or oblique fibres lie in between and connect the two layers ².

The ciliary body is supplied by the anterior ciliary arteries and the long posterior ciliary arteries which anastomose and form a vascular ring around the root of the iris. It is drained by the vorticose veins and then into the superior and inferior orbital veins.

The ciliary body receives parasympathetic innervation from the Edinger-Westphal nucleus in the midbrain and travels via the oculomotor nerve to the ciliary ganglion. This ganglion gives off short ciliary nerves which innervates the ciliary body.

Histology

The ciliary body contains two layers of cuboidal epithelium. The deep layer is heavily pigmented due to high vascularity and high level of melanin. The surface layer is non-pigmented, non-photosensitive extension of the receptor layer of the retina and is responsible for aqueous humour production ³.

Related pathology

• open-angle glaucoma

• angle-closure glaucoma

• endophthalmitis

• panophthalmitis

• ciliary body melanoma