The episclera is a thin vascular membrane between the conjunctiva and the sclera.
Episcleritis occurs in young adults, more commonly among women. It is usually idiopathic; it can be associated with connective tissue diseases and rarely with serious systemic diseases (present in about 15% of patients). (See also Overview of Conjunctival and Scleral Disorders Overview of Conjunctival and Scleral Disorders The conjunctiva lines the back of the eyelids (palpebral or tarsal conjunctiva), crosses the space between the lid and the globe (forniceal conjunctiva), then folds back on itself as it spreads... read more 
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Mild irritation occurs. Additionally, a bright red patch is present just under the bulbar conjunctiva (simple episcleritis). A hyperemic, edematous, raised nodule (nodular episcleritis) may also be present. The palpebral conjunctiva is normal.
Episcleritis is distinguished from conjunctivitis Overview of Conjunctivitis Conjunctival inflammation typically results from infection, allergy, or irritation. Symptoms are conjunctival hyperemia and ocular discharge and, depending on the etiology, discomfort and itching... read more by hyperemia localized to a limited area of the globe, much less lacrimation and no discharge. It is distinguished from scleritis Scleritis Scleritis is a severe, destructive, vision-threatening inflammation involving the deep episclera and sclera. Symptoms are moderate to marked pain, hyperemia of the globe, lacrimation, and photophobia... read more 
by lack of photophobia and lack of severe pain.
The condition is self-limited. If the review of systems does not suggest an underlying cause, unless the episode recurs, then a diagnostic assessment for systemic disorders is not routinely warranted.
Topical lubricating drops are typically used for patient comfort. A short course of topical corticosteroids (eg, prednisolone acetate, 1% drops 4 times a day for 7 days, gradually reduced over 3 to 4 weeks) or an oral nonsteroidal anti-inflammatory drug (NSAID) usually shortens the attack; corticosteroids are usually prescribed by an ophthalmologist. Topical vasoconstrictors (eg, tetrahydrozoline, brimonidine tartrate 0.025%) to improve appearance are optional; however, regular use can worsen erythema due to rebound vasodilation.
