Posterior Uveitis - Causes, Types, and Treatment.

Introduction:

The uvea is the area between the sclera and the retina in the eye. This area can be further divided into three parts:

• The iris (the color part of the eye).

• The ciliary body (part of the eye that helps in the lens positioning).

• The choroid (vascular layer of the eye).

Iris forms the anterior uvea, whereas the ciliary body and the choroid form the posterior uvea.

Uveitis is the inflammation of the middle layer of the eye. This inflammation is called posterior uveitis when it affects the posterior part of the uvea. Though the prevalence of posterior uveitis is only 10% among all the cases, it can cause significant damage to the eye structures. A variety of factors can cause posterior uveitis. As a result of the clinical presentation, symptoms and extent of the disease may vary. An in-depth understanding of posterior uveitis is necessary.

What Are the Causative Factors?

The causative factors of posterior uveitis depend upon the cause of inflammation. These factors are:

1. Infective Causes

Different bacterial and viral infections are responsible for this are:

• Toxoplasmosis.

• Toxocariasis.

• Tuberculosis (TB).

• Syphilis.

• Bartonella.

• Viral infections (herpes simplex, varicella zoster, human immunodeficiency virus).

2. Non-infectious Causes

• Acute posterior multifocal placoid pigment epitheliopathy (APMPPE).

• Multiple evanescent white dot syndrome (MEWDS).

• Geographic helicoid peripapillary choroidopathy (GHPC).

• Retinal pigment epitheliitis (Krill’s disease).

What Is Infectious Posterior Uveitis?

The diagnosis of infectious posterior uveitis is based on ocular imaging, systemic examination, and systemic evaluations.

1. Ocular Toxoplasmosis: It is mainly seen in tropical areas. Infection is transmitted from animals, raw meat, vegetables, or human-to-human contact. It can easily affect immunocompromised persons. Patients often complain of fever, skin rash, and muscle pain. Ocular symptoms are:

• Toxoplasmic Retinochoroiditis: Inflammation of the retina and choroid layer. Presence of white focal spots and scar tissue.

• Necrotizing Retinitis: Asymptomatic punched-out macular lesion with the central necrotizing zone.

• Kyrieleis Arteriolitis: Discrete or segmental inflammation of retinal blood vessels with the presence of peri arterial plaque and infiltration of inflammatory cells.

2. Ocular Toxocariasis: Children are mostly affected. Infection is transmitted from animals, especially dogs, through contaminated soil or food. Ocular symptoms are:

• Presence of granuloma (small area of inflammation) in retina and vitreous.

• Retinal detachment.

• Dead larvae are seen as white/ gray marks on the posterior pole.

• Damage of the optic nerve and nerve head.

• Endophthalmitis( purulent infection of the intraocular fluids).

3. Tubercular Posterior Uveitis: This is one of the most common bacterial infections in tropical areas. Infection is transmitted from the sputum and saliva of the infected persons. Affected persons complain of weight loss, cough, and blood during coughing. Ocular manifestations are:

• Disseminated Choroiditis or the presence of white or gray choroidal tubercles, which are .5 millimeters to 3 millimeters in diameter.

4. Ocular Syphilis: This is a bacterial infection that may spread through sexual contact or may affect an immunocompromised person suffering from the human immunodeficiency virus. Ocular manifestations are:

• Chorioretinitis: Infection of the pigmented vascular layer of the eye.

• Papilloedema: Swelling of the optic disc caused by increased intracranial pressure. Retinal detachment from the original position appears as salt and pepper.

5. Viral Retinitis: Viral infections like herpes simplex, varicella zoster, cytomegalovirus, and human immunodeficiency virus cause this.

• Viral Posterior Uveitis: Inflammation of the retina with multiple or single patches.

• Progressive Outer Retinal Necrosis: Typical cracked mud appearance is seen, characterized by retinal whiting, minimal inflammation of the posterior pole and vitreous humor, and scanty blood vessels.

• Acute Retinal Necrosis: This is a classical feature of herpetic infection characterized by necrosis of the retina and severe infection of the vitreous humor.

What Is Non-infectious Posterior Uveitis?

These conditions are non-infective and inflammatory, with a history of sudden onset. These conditions are:

1. Acute Posterior Multifocal Placoid Pigment Epitheliopathy:

This is a self-limiting condition with sudden onset of the disorder. This is characterized by the following:

• Multiple yellowish-white lesions in the retina.

• Atrophy of retinal pigmented epithelium.

• Swelling of the optic disc or optic edema.

2. Multiple Evanescent White Dot Syndrome (MEWDS):

This is also a self-limiting disease with a history of sudden onset and viral infection. Though the exact pathophysiology is not known, it can be identified by several key features:

• Presence of granules in macule.

• Only one eye is affected by sudden visual loss.

• Presence of white dots and spots in the retina.

• White dots and spots are present in the retina.

3. Geographic Helicoid Peripapillary Choroidopathy:

This is a rare chronic bilateral condition involving the retinal pigmented epithelium and choroid. The clinical features are:

• Irregular gray-white or creamy yellow infiltrates in the retina.

• Loss of vision in both eyes with a history of the appearance of flashes in the visual field.

• Presence of blind spot in the vision.

4. Acute Retinal Pigment Epitheliitis

Patients complain of blurred vision in the single eye. Clinical manifestations include:

• Clusters of hyper-pigmented dark gray spots in the retinal pigmented epithelium.

• Patients complain of distorted shapes of objects in the visual field.

How to Diagnose It?

There are different diagnostic tests to detect it.

• Optical Coherence Tomography: Cross-sectional tissue analysis is done through quasi-elastic (a method of energy transformation) compression of the tissue through reflected light.

• Indocyanine Green Angiography: Indocyanine dye is injected into the eye, after which an image of the retinal circulation is taken using white light and a fundus camera with a barrier filter.

• Fundus Fluorescein Angiography: In this method, sodium fluorescein dye is injected into the eye, and fundus images are taken with the help of a camera and a barrier filter. Unlike indocyanine angiography, Chorio capillary (small blood vessels of the retina ) images can not be taken in this method.

How to Manage It?

For the treatment of infective posterior uveitis, antibiotics are used.

• Antibacterial products like Verteporfin, long-acting Penicillin, Pyrimethamine, and Clindamycin can be used.

• For viral posterior uveitis, Acyclovir or Valacyclovir antiviral antibiotic is used. For noninfective uveitis cases, oral Prednisolone is used along with intravenous Methylprednisolone systemically.

• In severe cases, Azathioprine, Methotrexate, and Mycophenolate Mofetil, T-cell suppressors such as Cyclosporine and Tacrolimus are administered as immunosuppressive agents.

Conclusion:

Uvea is situated between the sclera and retina of the eye. Different pathological conditions cause posterior uveitis. Identification of causative factors is important to determine the treatment protocols. Modern diagnostic aids are also useful for proper imaging to identify pathological changes. Antibacterial medications and proper care helps in healing this condition faster.