Retinochoroiditis

Retinochoroiditis (re·ti·no·cho·roid·i·tis), from the Latin rete (net) and Greek chorion (skin) + -itis (inflammation), is an inflammation of both the retina and the choroid (the choroid coat) of the eye. Due to the shared blood supply of these two layers, inflammation of one often leads to the inflammation of the other. The condition is also frequently referred to as chorioretinitis, with the terms often used interchangeably.

Anatomy and Pathology

The eye is composed of several layers. The retina is the light-sensitive layer of tissue at the back of the inner eye that acts like the film in a camera. It converts light into neural signals and sends them to the brain for visual recognition. The choroid is the vascular layer of the eye, sandwiched between the retina and the sclera (the white of the eye). It is rich in blood vessels and is responsible for supplying oxygen and nutrients to the outer portion of the retina.

In retinochoroiditis, inflammatory cells damage both of these crucial layers. The inflammation can lead to scarring of the retina and choroid, which can cause vision problems. The severity of vision loss depends on the location and extent of the scarring. Lesions in the macula, the central part of the retina responsible for sharp, detailed vision, are the most debilitating.

Causes

Retinochoroiditis is not a disease in itself but a manifestation of an underlying condition. The causes are diverse and can be infectious or non-infectious.

Infectious causes are the most common and include:

Toxoplasmosis: Caused by the parasite Toxoplasma gondii, this is the most frequent cause of retinochoroiditis globally. It can be congenital (passed from mother to child during pregnancy) or acquired.
Cytomegalovirus (CMV): A common virus that can cause serious eye disease, particularly in immunocompromised individuals, such as those with HIV/AIDS or organ transplant recipients.
Tuberculosis: The bacterium Mycobacterium tuberculosis can spread to the eye and cause inflammation.
Syphilis: The sexually transmitted infection caused by Treponema pallidum.
Herpes Simplex Virus (HSV) and Varicella-Zoster Virus (VZV): These viruses can cause a condition known as acute retinal necrosis.
Fungal infections: Such as Candida or Aspergillus, especially in individuals with weakened immune systems.

Non-infectious causes are typically autoimmune or inflammatory in nature and can include conditions such as:

Sarcoidosis
Behçet's disease
Vogt-Koyanagi-Harada syndrome
Birdshot chorioretinopathy

In some cases, the cause is unknown (idiopathic).

Symptoms

Symptoms of retinochoroiditis can vary depending on the location and severity of the inflammation but often include:

Floaters: Specks or lines that drift through the field of vision.
Blurred vision.
Photophobia: Sensitivity to light.
Scotoma: A blind or dark spot in the field of vision.
Pain and redness in the eye, although this is less common.

Diagnosis and Treatment

Diagnosis is made by an ophthalmologist through a comprehensive eye examination, which includes a dilated fundus exam to view the retina and choroid. Imaging tests like fundus photography, optical coherence tomography (OCT), and fluorescein angiography can help assess the extent of the inflammation and damage. Blood tests and sometimes analysis of the eye's fluid may be necessary to identify the underlying cause.

Treatment is directed at the underlying cause of the inflammation.

For infectious causes, antimicrobial medications are prescribed. For example, toxoplasmosis is treated with a combination of antiparasitic drugs, while viral causes are treated with antiviral medications.
For non-infectious, autoimmune causes, treatment focuses on suppressing the immune system with corticosteroids (administered as eye drops, injections, or orally) and other immunosuppressive drugs.

The goal of treatment is to reduce inflammation, prevent further damage to the retina and choroid, and preserve vision.

Comparison with Chorioretinopathy

While retinochoroiditis is an inflammatory condition (indicated by the suffix -itis), chorioretinopathy (from Greek pathos, suffering or disease) is a broader, non-specific term that refers to any disease or disorder of the choroid and retina.

Retinochoroiditis specifically implies active inflammation is the cause of the pathology.
Chorioretinopathy encompasses non-inflammatory conditions as well. A key example is central serous chorioretinopathy, a condition where fluid builds up under the retina without primary inflammation, leading to visual distortion. Other chorioretinopathies can be caused by degenerative processes, trauma, or vascular abnormalities.

In essence, retinochoroiditis is a type of chorioretinopathy, but not all chorioretinopathies are inflammatory like retinochoroiditis.