Uvea

Anatomical structure of the eye

The uvea is the middle layer of the eye, situated between the sclera and the retina. It is a critical component of the eye, playing a vital role in providing nutrients to the eye and controlling the amount of light that enters it. The uvea is composed of three main parts: the iris, the ciliary body, and the choroid.

Diagram of the human eye showing the uvea.

Iris

The iris is the colored part of the eye that surrounds the pupil. It is responsible for controlling the diameter and size of the pupil, thus regulating the amount of light that reaches the retina. The iris contains two groups of smooth muscles: the sphincter pupillae and the dilator pupillae, which constrict and dilate the pupil, respectively.

Ciliary Body

The ciliary body is located behind the iris and is responsible for producing the aqueous humor, the fluid in the eye. It also contains the ciliary muscle, which alters the shape of the lens to focus light on the retina, a process known as accommodation.

Choroid

The choroid is a vascular layer of the eye containing connective tissue, and it lies between the retina and the sclera. It provides oxygen and nutrients to the outer layers of the retina. The choroid is rich in blood vessels and is heavily pigmented, which helps to absorb excess light and prevent it from scattering within the eye.

Function

The uvea plays several crucial roles in the eye:

• Nutrient Supply: The choroid supplies nutrients and oxygen to the outer layers of the retina.
• Light Regulation: The iris controls the amount of light entering the eye by adjusting the size of the pupil.
• Accommodation: The ciliary body adjusts the lens for focusing on objects at various distances.

Clinical Significance

Disorders of the uvea can lead to significant eye problems. Some common conditions include:

• Uveitis: Inflammation of the uvea, which can cause pain, redness, and vision problems.
• Glaucoma: Increased intraocular pressure can affect the uvea, particularly the ciliary body.
• Cataracts: Changes in the lens can affect the function of the ciliary body.

Related pages

• Eye
• Retina
• Sclera
• Lens (anatomy)