Circumscribed, usually segmental, and generally nodular inflammation of the episclera (connective tissue between sclera and conjunctiva).
Episcleritis is the most common form of scleral inflammation.
Episcleritis is rarely attributable to one of the systemic underlyingdisorders listed in Table 6.1, and is only occasionally due to bacterial or viral inflammation. Often episcleritis will have no readily discernible cause.
Episcleritis can be unilateral or bilateral. It is usually associatedwith segmental reddening and slight tenderness to palpation.
The episcleral vessels lie within the fascial sheath of the eyeball(Tenon’s capsule) and are arranged radially. In episcleritis, these vessels and the conjunctival vessels above them become hyperemic (Fig. 6.2). Tenon’s capsule and the episclera are infiltrated with inflammatory cells, but the sclera itself is not swollen. The presence of small mobile nodules is typical of nodular episcleritis.
The disorder should be distinguished from conjunctivitis (see next paragraph) and scleritis (6.6.2).
The conjunctival blood vessels are the most superficial; the episcleral vessels lie within Tenon’s capsule and are arranged radially. When vaso-constrictive eyedrops are applied, the conjunctival injection will disap-pear but not the episcleral injection. This makes it possible to distin-guish conjunctivitis from episcleritis.
Episcleritis usually resolves spontaneouslywithin one to two weeks, although the nodular form can persist for extended periods of time. Severe symptoms are treated with topical steroids (eyedrops) or with a nonsteroidal anti-inflammatory agent.