Often misdiagnosed as conjunctivitis, episcleritis and scleritis are inflammatory disorders of the white part of the eye that cause redness and pain. Any redness of the eye associated with discomfort should be seen by your optometrist so that the correct diagnosis made and the most appropriate treatment instigated.
Episcleritis is generally milder than scleritis and does not have the same potential to cause vision loss. This condition involves inflammation of the tissue between the surface of the eye and the depper structural tissue (sclera). It can sometimes be isolated to only a certain sector of the eye. Instillation with a blood-vessel constricting agent like phenylephrine will shrink only the inflamed episcleral vessels and differentiate episcleritis from the more sight-threatening scleritis. Most cases occur without cause (idiopathic) but up to 30% of cases may be related to a systemic condition such as inflammatory bowel disease or connective tissue disease. Most episcleritis is self-limiting but often your optometrist will prescribe anti-inflammatory drops to speed up the recovery.
Scleritis is a more severe inflammatory condition affecting the collagen support of the eye - the sclera. Scleritis is often characterised by a deep pain, often at level intense enough to wake you at night. Diagnosis is helped with examination under natural light - the deeper inflamed vessels have a characteristic purple hue. Fortunately the condition is rare, but like episcleritis, it can often be associated with underlying autoimmune disease such as inflammatory arthritis, lupus, certain connective tissue diseases, inflammatory bowel disease, Sjogren's syndrome, Wegener's granulomatosis or scleroderma. The severity and treatment of scleritis varies depending of the depth of tissue affected, with some forms of scleritis leading to permanent vision loss.
CAPTION: The parts of the eye affected in scleritis and episcleritis (courtesy of http://www.bupa.co.uk/health-information/directory/s/scleritis)