Ciliary Definition

Located within the eye’s posterior chamber, the ciliary body is a ring-shaped thickening of the tissue that separates the posterior chamber from the vitreous body. The ciliary muscle, arteries, and fibrous connective tissue are all found in this region. Called ciliary processes, folds on the inner ciliary epithelium of the eyelid discharge aqueous humour into the posterior chamber when the eyelid is closed. After that, the aqueous humour passes past the pupil and into the anterior chamber of the eye.

For the ciliary body to be linked to the lens, connective tissue known as zonular fibres must be present (fibres of Zinn). Relaxation of the ciliary muscle causes tension in these fibres, which alters the curvature of the lens, allowing light to be focused on the retina when the eye is closed.

The inner layer is translucent and covers the vitreous body; it is connected with the neural tissue of the retina. The outer layer is opaque and covers the optic nerve. A highly pigmented layer that is continuous with the retinal pigment epithelium and which contains the cells of the dilator muscle is present on the surface of the retina. This double membrane is frequently assumed to be continuous with the retina and to be a rudiment of the embryological counterpart to the retina, however, this is not the case. The inner layer is pigment less until it reaches the iris, at which point it begins to take on pigment. The ora Serrata is the point at which the retina comes to an end.

Ciliary body

A portion of the middle layer of the eye’s wall is visible. Located behind the iris, the ciliary body houses a ring-shaped muscle that alters the curvature of the lens as the eye concentrates. It is also responsible for the production of the clear fluid that fills the gap between the cornea and the iris.

Function

The ciliary body performs three functions: accommodation, generation and resorption of aqueous humour, and maintenance of the lens zonules to fix the lens in place.

Accommodation

Accommodation simply implies that when the ciliary muscle contracts, the lens becomes more convex, which improves the focus on things that are closer to the eye. When it relaxes, it flattens the lens, which in general improves the focus for faraway objects.

Aqueous humour

Because the lens and the cornea do not have their blood supply, aqueous humour is produced by the ciliary epithelium of the ciliary processes. Aqueous humour is important for giving oxygen, nutrients, and metabolic waste disposal to the lens and cornea. Aqueous humour production is carried out by active secretion mechanisms (the Na+K+ATPase enzyme establishing an osmotic gradient for the passage of water into the posterior chamber) and by ultrafiltration of plasma, with active secretion mechanisms accounting for 80% of total production. The rate of ultrafiltration is affected by intraocular pressure, but not the rate of secretion.

Lens zonules

The suspensory ligament of the lens is made up of zonular fibres that are connected. These are responsible for providing strong attachments between the ciliary muscle and the lens capsule.

Conclusion

The ciliary body of the eye is a muscle that is placed between the sclera (white of the eye) and the tiny ligaments that support the lens of the eye. It is responsible for maintaining the shape of the lens of the eye. It is composed of both longitudinal and circular fibres, and its function is to alter the curvature of the lens, allowing the eye to concentrate on objects that are either close to or far away from the lens.