|Classification and external resources|
Episcleritis is a benign, self-limiting inflammatory disease affecting part of the eye called the episclera. The episclera is a thin layer of tissue that lies between the conjunctiva and the connective tissue layer that forms the white of the eye (sclera). Episcleritis is a rare disease, and is characterized by the abrupt onset of eye pain and redness.
There are two types of episcleritis, one where the episclera is diffusely affected (diffuse episcleritis), and the other where nodules are present in the episclera (nodular episcleritis). Most cases have no identifiable cause, although a small fraction of cases are associated with various systemic diseases. Often people with episcleritis experience it recurrently. Treatment focuses on decreasing discomfort, and includes lubricating eye drops. More severe cases may be treated with topical corticosteroids or oral anti-inflammatory medications (NSAIDs).
Signs and symptoms 
Symptoms of episcleritis include mild eye pain, redness, and watery eyes. The pain of episcleritis is less severe than in scleritis. The redness may include the entire episclera (diffuse), or it may be nodular, involving only a small, well-circumscribed area (sectoral). The diffuse type of episcleritis may be less painful than the nodular type. Sometimes, small nodules are present within the episclera, which move slightly over the sclera with gentle pressure.
Discharge is absent with episcleritis, and vision is unaffected. Patients with episcleritis experience far less photophobia than patients with uveitis. Episcleritis does not cause the presence of cells or flare in the anterior chamber of the eye.
Most of the time, episcleritis is idiopathic, which means its cause remains unknown. An identifiable cause is discovered in only one third of cases. Several diseases are associated with episcleritis, including systemic vasculitic diseases (polyarteritis nodosa, Wegener's granulomatosis), connective tissue diseases (rheumatoid arthritis), rosacea, atopy, gout, and ulcerative colitis. 59 percent of patients with relapsing polychondritis have either episcleritis or scleritis. Rarely, episcleritis may be caused by scleritis.
The redness in the eye associated with episcleritis is due to engorgement of the large episcleral blood vessels, which run in a radial direction from the limbus. Typically, there is no uveitis, or thickening of the sclera.
The diagnosis of episcleritis is based upon the history and physical examination. The history should be explored for the presence of the diseases associated with episcleritis, and the symptoms they cause, such as rash, arthritis, venereal disease, and recent viral infection. Episcleritis may be differentiated from scleritis by using phenylephrine or neosynephrine eye drops, which causes blanching of the blood vessels in episcleritis, but not in scleritis. A blue color to the sclera suggests scleritis, rather than episcleritis.
After anesthetizing the eye with medication, the conjunctiva may be moved with a qtip to observe the location of the enlarged blood vessels.
Often, treatment is not necessary, because episcleritis is a self-limiting condition. Artificial tears may be used to help with irritation and discomfort. More severe cases can be treated with either topical corticosteroids or oral non-steroidal anti-inflammatory drugs.
Episcleritis is a rare disease, and its exact prevalence and incidence are unknown. It typically affects young adults, and may be more common in women.
Episcleritis is a benign, self-limiting condition, meaning patients recover without any treatment. Most cases of episcleritis resolve within 7-10 days. The nodular type is more aggressive and takes longer to resolve. Although rare, some cases may progress to scleritis. However, in general, episcleritis does not cause complications in the eye.
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