Uveitis overview

# Overview
Uveitis specifically refers to inflammation of the middle layer of the eye, termed the "uvea". In common usage, it may refer to an inflammatory process involving the interior of the eye. The uvea consists of the iris, ciliary body, and choroid; it provides most of the blood supply to the retina. Uveitis may occur unilaterally or bilaterally, affect the anterior, intermediate, or posterior segment of the eye, may be infectious or non infectious, and granulomatous or non-granulomatous. The exact pathogenesis of uveitis is not fully understood. It is thought that uveitis is mediated by a genetic predisposition and an acquired cross immunity to infectious agents, or cross immunity to self-antigens due to underlying autoimmune diseases. Common causes of uveitis include seronegative spondyloarthropathy, sarcoidosis, juvenile idiopathic arthritis, systemic lupus erythematosus, Behcet syndrome, multiple sclerosis, AIDS, syphilis, and tuberculosis. Uveitis must be differentiated from other diseases such as conjunctivitis, endophthalmitis, or scleritis. A history of cigarette smoking is associated with all etiologies and subtypes of uveitis. Uveitis is estimated to be responsible for approximately 10% of the blindness in the United States. If left untreated uveitis can progress to permanent vision loss or result in complications such as cataracts, glaucoma, and retinal detachment. A history of an underlying associated condition along with symptoms of eye pain, redness, photophobia, floaters, and blurry vision is strongly suggestive of uveitis. There are no specific laboratory or physical examination findings associated with uveitis. Imaging modalities may assist in diagnosing an underlying condition, though have no diagnostic utility for uveitis itself. Slit lamp test is the diagnostic modality of choice. Other ophthalmologic studies may assist in further characterizing the disease. Mainstay medical therapy is by high dose corticosteroids. Targeted antimicrobials may be required to treat an underlying infection. Surgical intervention is reserved for managing complications of uveitis such as cataract surgery or glaucoma surgery. The only indicated guideline for screening is in patients suspected of or diagnosed with juvenile idiopathic arthritis. Prompt treatment of a potential underlying infection may help prevent development of uveitis.

# Historical Perspective
Uveitis was first discovered by Hippocrates, a Greek physician, and was a well known to other major medical physicians, such as Galen and Aetius of Amida. In 1952, corticosteroids were used to treat uveitis for the first time.

# Classification
Uveitis is best described using various, concurrent classification systems. Uveitis may be classified according to anatomical location into 4 subtypes, depending on which part of the uvea is primarily affected: anterior, intermediate, posterior, and panuveitis. Based on the duration of symptoms it may be further sub-classified as acute or chronic. Upon further investigation, uveitis may be classified according to histological features of the inflammation such as granulomatous or non-granulomatous. Additionally, uveitis may be described by the laterality of the condition (unilateral or bilateral). Finally, uveitis may be classified by general underlying systemic causes such as infectious, autoimmune, drug-induced, or idiopathic.

# Pathophysiology
The exact pathogenesis of uveitis is not fully understood. It is thought that uveitis is mediated by a genetic predisposition and an acquired cross immunity to infectious agents, or cross immunity to self-antigens due to underlying autoimmune diseases. It is estimated that 35% to 50% of cases of uveitis are idiopathic. Development of uveitis is hypothesized to be the result of a genetic predisposition for acquiring the disease; contributions of several human leukocyte antigen (HLA) alleles are most commonly implicated.

# Causes
Common causes of uveitis include seronegative spondyloarthropathy, sarcoidosis, juvenile idiopathic arthritis, systemic lupus erythematosus, Behcet syndrome, multiple sclerosis AIDS, syphilis, and tuberculosis.

# Differentiating Uveitis from Other Diseases
Uveitis must be differentiated from other diseases that cause conjunctival injection, eye pain, photophobia, or visual disturbance. Masquerade syndromes, which are ophthalmic disorders that clinically present as either an anterior or posterior uveitis but are not primarily inflammatory, must be differentiated from uveitis. As uveitis manifests in a variety of clinical etiologies, differentiation must also be established in accordance with the particular subtype.

# Epidemiology and Demographics
Worldwide, the prevalence of uveitis ranges from 69 to 204 per 100,000 persons. The prevalence among different subtypes of uveitis varies greatly. Anterior, chronic, non-granulomatous and non-infectious subtypes are more commonly seen than others. The worldwide incidence of uveitis ranges from 17 to 52 per 100,000 persons per year. The age, sex, and race distribution is also dictated by the prevalence of the underlying cause within those demographic groups.

# Risk Factors
A history of cigarette smoking is associated with all etiologies and subtypes of uveitis. Some underlying causes have specific potent risk factors for developing uveitis such as seronegative spondyloarthropathies, immunosuppression, sarcoidosis, and juvenile idiopathic arthritis.

# Screening
There is insufficient evidence to recommend routine screening for uveitis for the general population. For patients diagnosed with or suspected of having juvenile idiopathic arthritis (JIA), screening guidelines have been recommended by the American Academy of Pediatrics (AAP) and the British Society of Paediatrics and Rheumatology (BSPAR).

# Natural History, Complications and Prognosis
If left untreated, uveitis can  progress to permanent vision loss. Complications of uveitis include cataracts, glaucoma, macular edema, and retinal detachment. With appropriate treatment, most attacks of anterior uveitis resolve within days to weeks, however, relapses are common. Inflammation related to posterior uveitis may last from months to years and may cause permanent vision damage, even with treatment. 

# Diagnosis

## History and Symptoms
Obtaining a complete history is an important aspect of making a diagnosis of uveitis. It provides insight into cause, precipitating factors, and associated underlying conditions. Uveitis can present unilaterally or bilaterally. Symptoms may develop acutely or insidiously, and may vary depending on the underlying etiology of the uveitis. Acute uveitis attacks are more commonly symptomatic and affect the anterior chamber. Symptoms of anterior uveitis include eye pain, eye redness, and photophobia. Intermediate, posterior, and panuveitis commonly present with floaters, blurry vision, and impaired vision. Chronic uveitis usually has an indolent courses and may not present with eye pain or redness.

## Physical Examination
A complete medical history and comprehensive eye examination must be performed by an optometrist or ophthalmologist to properly diagnosis uveitis. Eye examination of patients with uveitis is usually remarkable for eye redness and increased or decreased intraocular pressure. Depending on the affected anatomy of the uvea, "snowbanking" or optic disc edema may be seen on dilated fundus exam, and mutton fat keratic precipitates on slit lamp test may also be appreciated. A complete physical examination can provide insight into the cause, and associated underlying conditions.

## Laboratory Findings
There are no diagnostic lab findings associated with uveitis. The presence of certain non-specific laboratory findings, in the presence of uveitis, may be suggestive of certain underlying causes. Examples of tests that may demonstrate abnormal findings include CBC, ESR, CRP, complete metabolic panel, iron studies, and serology titers.

## X Ray
There are no diagnostic x ray findings associated with uveitis. Positive x ray findings may be found in underlying conditions such as sarcoidosis, tuberculosis, and seronegative spondyloarthropathies.

## CT
There are no diagnostic CT scan findings associated with uveitis. The presence of certain CT findings, in the presence of uveitis, may be suggestive of specific underlying causes such as inflammatory bowel disease, sarcoidosis, and Behcet's disease.

## MRI
There are no diagnostic MRI findings associated with uveitis. The presence of certain MRI findings, in the presence of uveitis, may be suggestive of specific underlying causes such as sarcoidosis, multiple sclerosis, Behcet's disease, syphilis, and joint abnormalities in seronegative spondyloarthropathies.

## Ultrasound
There are no diagnostic ultrasound findings associated with uveitis.

## Other Imaging Findings
There are no other diagnostic imaging findings associated with uveitis.

## Other Diagnostic Studies
Other diagnostic studies associated with uveitis include slit lamp test and ocular tonometry. The slit lamp test is considered a gold standard modality in diagnosing uveitis. While intraocular pressure may increase or decrease depending on the anatomical location and severity of the inflammation, slit lamp test findings are relatively more consistent. Common slit lamp test findings include presence of inflammatory cells in the anterior chamber, keratic precipitates, and mutton fat precipitates. Slit lamp test findings associated with anatomical location include snowbanking in intermediate uveitis (e.g., pars planitis), snowballing in vitritis, and retinal edema in posterior uveitis.

# Treatment

## Medical Therapy
The mainstay of therapy for uveitis is steroids, either as topical eye drops or oral therapy with prednisolone.  Acyclovir is the drug of choice for empiric therapy in anterior uveitis.  The treatment for intermediate and posterior uveitis generally depends on the underlying disease.

## Surgery
There is no  indication for surgical intervention in uveitis. Surgical management of uveitis is most commonly reserved for management of complications of uveitis or, rarely, for diagnostic purposes. Common complications of uveitis requiring surgery include cataract surgery, glaucoma surgery, or band keratopathy. Common indications for the diagnostic utility of surgery in uveitis include vitreous tap, vitreous biopsy, and posterior uveal biopsy.

## Primary Prevention
Appropriate treatment of an underlying disorder may help to prevent uveitis in persons with a systemic infection or inflammatory disease.

## Secondary Prevention
There are no secondary prevention methods associated with uveitis.