What is the Uvea?

The uvea is the middle layer of the eye, situated between the sclera (the white outer layer) and the retina (the inner layer). It consists of three key parts: the iris, the ciliary body, and the choroid. The uvea plays a crucial role in supplying blood to the eye, controlling light entry, and maintaining the eye's health. Inflammation or diseases of the uvea can lead to serious eye conditions, including vision loss.

Structure of the Uvea

The uvea is composed of three interconnected parts:

1. Iris:
   The colored part of the eye that surrounds the pupil. It regulates the amount of light entering the eye by controlling the size of the pupil.

2. Ciliary Body:
   Located behind the iris, the ciliary body produces aqueous humor (the clear fluid in the eye) and controls the shape of the lens, helping the eye focus on near or distant objects.

3. Choroid:
   A vascular layer between the retina and the sclera, the choroid contains blood vessels that nourish the outer layers of the retina. It helps to maintain the temperature and health of the eye.

Functions of the Uvea

The uvea serves several essential functions in the eye:

• Regulating Light: The iris adjusts the size of the pupil, controlling how much light enters the eye, which is critical for clear vision in varying light conditions.
• Focusing Vision: The ciliary body helps in focusing vision by changing the shape of the lens to adjust for near or far objects (accommodation).
• Nourishing the Eye: The choroid provides oxygen and nutrients to the retina, ensuring the retina's health and proper functioning.
• Producing Eye Fluid: The ciliary body also produces the aqueous humor, which maintains intraocular pressure and provides nutrients to the front part of the eye.

Conditions Affecting the Uvea

Several conditions can affect the uvea, the most common being uveitis, which refers to inflammation of the uvea. Uveitis can lead to pain, redness, blurred vision, and even blindness if untreated. Other conditions affecting the uvea include:

1. Uveitis:
   Inflammation of the uvea can be caused by infections, autoimmune disorders, trauma, or exposure to toxins. Uveitis can occur in one or more parts of the uvea:

   • Anterior Uveitis: Inflammation of the iris (iritis) or iris and ciliary body (iridocyclitis). This is the most common type of uveitis.
   • Intermediate Uveitis: Inflammation of the ciliary body and the vitreous humor (the gel inside the eye).
   • Posterior Uveitis: Inflammation of the choroid, often affecting the retina and optic nerve as well.

2. Choroidal Neovascularization (CNV):
   Abnormal blood vessels develop in the choroid and can cause vision loss. CNV is often associated with conditions like age-related macular degeneration.

3. Iris Tumors:
   Benign or malignant tumors can form in the iris, affecting its structure and potentially leading to vision issues.

4. Ciliary Body Melanoma:
   A rare but serious cancer that affects the ciliary body. It may cause blurred vision, pain, or pressure in the eye.

Symptoms of Uveal Disorders

Uveal disorders, particularly uveitis, can cause a range of symptoms depending on the part of the uvea affected. Common symptoms include:

• Eye redness.
• Eye pain or discomfort.
• Blurred vision.
• Sensitivity to light (photophobia).
• Dark spots or "floaters" in the vision.
• Decreased vision.
• Headaches (in some cases of anterior uveitis).

Diagnosis of Uveal Disorders

Diagnosing uveal conditions often requires a comprehensive eye exam by an ophthalmologist, including:

• Slit-lamp Examination: A microscope with a light source is used to examine the front part of the eye, including the iris and ciliary body.
• Ophthalmoscopy: A device is used to examine the retina and choroid, looking for inflammation or abnormal blood vessels.
• Fluorescein Angiography: A dye is injected into the bloodstream to highlight blood vessels in the retina and choroid, useful in diagnosing choroidal neovascularization.
• Optical Coherence Tomography (OCT): A non-invasive imaging test that provides detailed cross-sectional images of the retina and choroid.

Treatment for Uveal Conditions

Treatment for uveal disorders depends on the underlying cause and severity. Common treatment options include:

1. Medications:

   • Corticosteroids: Used to reduce inflammation in cases of uveitis. They may be administered as eye drops, oral medication, or injections.
   • Immunosuppressive Drugs: Prescribed for severe or chronic uveitis to control the immune response.
   • Antibiotics or Antivirals: If the uveitis is caused by an infection, appropriate medication is prescribed to treat the underlying infection.

2. Laser Therapy:
   Laser treatment may be used to treat certain conditions affecting the choroid, such as choroidal neovascularization or to control bleeding from abnormal blood vessels.

3. Surgery:
   In cases where medical treatment is not effective, surgical options such as vitrectomy (removal of the vitreous gel) or the removal of tumors from the iris or ciliary body may be necessary.

Preventing Uveal Disorders

While not all uveal conditions can be prevented, certain steps can help reduce the risk of developing issues such as uveitis:

• Regular Eye Exams: Routine eye exams can help detect uveal conditions early, before they lead to significant damage.
• Managing Systemic Conditions: Autoimmune disorders, infections, and other systemic health issues can increase the risk of uveitis. Managing these conditions through proper medical care can reduce the likelihood of eye involvement.
• Wearing Eye Protection: Protecting the eyes from trauma or exposure to chemicals or toxins can prevent some cases of uveitis and other uveal disorders.