Retinitis

Retinitis (/rɛtɪˈnaɪtɪs/) is the inflammation of the retina, the light-sensitive tissue lining the back of the eye. The term originates from the Latin rete ("net"), describing the retina's appearance, and the Greek suffix -itis, denoting inflammation.

Retinitis is not a single disease but a broad term for a range of conditions that can damage the retina and lead to vision loss. The inflammation can be caused by infections, autoimmune disorders, or genetic conditions. Depending on the cause and the area of the retina affected, symptoms can range from minor visual disturbances to permanent blindness.

Signs and Symptoms

The symptoms of retinitis vary depending on the specific cause and severity but commonly include:

Blurred vision
Floaters: Specks, webs, or lines drifting in the field of vision.
Scotoma: A partial loss of vision or a blind spot.
Photopsia: Seeing flashes of light.
Loss of peripheral vision, sometimes called "tunnel vision."
Loss of central vision, which affects the ability to see fine detail.
Nyctalopia: Difficulty seeing in low light or at night.

Causes and Types

Retinitis is generally categorized by its underlying cause.

1. Infectious Retinitis

Inflammation is triggered by a pathogen that has invaded the retinal tissue. Treatment typically involves antimicrobial medications.

Viral Retinitis: This is one of the most common infectious forms.
- Cytomegalovirus (CMV) Retinitis: Occurs most often in individuals with compromised immune systems, such as those with HIV/AIDS or organ transplant recipients. It can be aggressive and lead to retinal detachment and blindness if not treated promptly with antiviral drugs.
- Herpetic Retinitis: Caused by the Herpes Simplex Virus (HSV) or Varicella-Zoster Virus (VZV, the cause of chickenpox and shingles), leading to conditions like Acute Retinal Necrosis (ARN).
Parasitic Retinitis:
- Ocular Toxoplasmosis: Caused by the parasite Toxoplasma gondii, it is a leading cause of posterior uveitis (inflammation in the back of the eye) worldwide. It often presents as a focal area of retinitis with overlying inflammation in the vitreous humor.
Bacterial and Fungal Retinitis: Less common causes include bacteria (from infections like syphilis or tuberculosis) and fungi (like Candida), which can spread to the eye through the bloodstream.

2. Non-Infectious (Autoimmune) Retinitis

This type occurs when the body's own immune system mistakenly attacks the retina. It is often associated with systemic autoimmune diseases.

Examples include retinitis seen in patients with lupus, Behçet's disease, sarcoidosis, and Vogt-Koyanagi-Harada (VKH) syndrome.
Treatment involves corticosteroids and other immunosuppressive drugs to control the inflammation.

3. Retinitis Pigmentosa (A Special Case)

Despite its name, Retinitis Pigmentosa (RP) is not a classic inflammatory disease. It is a group of inherited genetic disorders that cause the progressive degeneration and death of photoreceptor cells (rods and cones) in the retina.

Primary Symptoms: The breakdown of rod cells typically occurs first, leading to early symptoms of night blindness and a gradual loss of peripheral vision.
Progression: Over years or decades, the disease can affect cone cells, leading to the loss of central and color vision.
Appearance: The condition gets its name from the characteristic clumps of dark pigment that can deposit in the retina as the cells degenerate.
Treatment: There is no cure for RP, but treatments focus on slowing its progression (e.g., through vitamin A supplementation in some cases), managing symptoms with low-vision aids, and exploring advanced therapies like gene therapy and retinal prostheses.

Diagnosis

Diagnosing retinitis involves a comprehensive eye examination, including:

Dilated Fundus Examination: An ophthalmologist uses an ophthalmoscope to view the retina, optic nerve, and blood vessels directly to look for signs of inflammation, lesions, or pigment changes.
Imaging: Techniques like Optical Coherence Tomography (OCT) provide detailed cross-sectional images of the retina to assess swelling and damage. Fluorescein angiography involves injecting a dye to visualize retinal blood flow and identify leakage or abnormalities.
Visual Field Testing: Measures the full extent of a patient's peripheral vision to map any blind spots.
Laboratory Tests: If an infection or autoimmune disease is suspected, blood tests or analysis of fluid from the eye (vitreous or aqueous humor) may be performed to identify the causative agent or specific antibodies.