How is conjunctivitis separated clinically from episcleritis and scleritis?
Conjunctivitis is the most common cause of a red eye presenting to clinicians. Common etiologies include allergies, viral and bacterial infections, and local irritation (e.g., severe dryness), although it can also occur secondary to inflammatory disease (e.g., reactive arthritis). Conjunctivitis stemming from common etiologies is often bilateral and involves the palpebral and bulbar surfaces. In contrast, episcleritis and scleritis are commonly limited to the globe/bulbar surface and are often sectoral in location. Conjunctival vessels lie loosely on the superficial bulbar surface and can be moved across the underlying scleral surface by a cotton swab, helping the clinician to distinguish redness originating from one of these sites.
