Uvea

Uvea

The uvea is the middle layer of the eye, situated between the outer fibrous layer (the sclera and cornea) and the inner sensory layer (the retina). It is composed of three main parts: the iris, the ciliary body, and the choroid.

Diagram of the human eye, showing the uvea.

Structure

The uvea is a highly vascular structure, providing most of the blood supply to the eye. It is responsible for various functions, including controlling the amount of light entering the eye, focusing the lens, and nourishing the retina.

Iris

The iris is the colored part of the eye, surrounding the pupil. It controls the diameter and size of the pupil and thus the amount of light reaching 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 the production of aqueous humor, the fluid in the anterior segment of the eye. It also contains the ciliary muscle, which changes the shape of the lens to focus light on the retina, a process known as accommodation.

Choroid

The choroid is a layer of blood vessels and connective tissue between the sclera and the retina. It provides oxygen and nutrients to the outer layers of the retina. The choroid is heavily pigmented, which helps to absorb excess light and prevent reflections within the eye.

Function

The primary functions of the uvea include:

• **Regulation of light entry**: The iris adjusts the size of the pupil to control the amount of light entering the eye.
• **Accommodation**: The ciliary body adjusts the lens shape for focusing on near or distant objects.
• **Nourishment**: The choroid supplies blood to the retina and other parts of the eye.

Clinical Significance

The uvea can be affected by various diseases, most notably uveitis, which is an inflammation of the uveal tract. Uveitis can lead to symptoms such as redness, pain, light sensitivity, and blurred vision. It can be caused by infections, autoimmune disorders, or trauma.

Related Pages

• Eye
• Iris (anatomy)
• Ciliary body
• Choroid
• Uveitis

References

• "Uvea." Wikipedia, The Free Encyclopedia. https://en.wikipedia.org/wiki/Uvea
• "Anatomy of the Eye." American Academy of Ophthalmology. https://www.aao.org/eye-health/anatomy