Reactive arthritis is highly associated with HLA-B27. Conjunctivitis is associated with the autoimmune disease relapsing polychondritis. Diagnosis
Cultures are not often taken or needed as most cases resolve either with time or typical antibiotics. If bacterial conjunctivitis is suspected, but no response to topical antibiotics is seen, swabs for bacterial culture should be taken and tested. Viral culture may be appropriate in epidemic case clusters.A patch test is used to identify the causative allergen in allergic conjunctivitis.Although conjunctival scrapes for cytology can be useful in detecting chlamydial and fungal infections, allergy, and dysplasia, they are rarely done because of the cost and the general dearth of laboratory staff experienced in handling ocular specimens. Conjunctival incisional biopsy is occasionally done when granulomatous diseases (e.g., sarcoidosis) or dysplasia are suspected. Classification
Conjunctivitis may be classified either by cause or by extent of the inflamed area. Causes
Allergy
Bacteria
Viruses
Chemicals
AutoimmuneNeonatal conjunctivitis is often grouped separately from bacterial conjunctivitis because it is caused by different bacteria than the more common cases of bacterial conjunctivitis. By extent of involvement
Blepharoconjunctivitis is the dual combination of conjunctivitis with blepharitis (inflammation of the eyelids). Keratoconjunctivitis is the combination of conjunctivitis and keratitis (corneal inflammation). Blepharokeratoconjunctivitis is the combination of conjunctivitis with blepharitis and keratitis. It is clinically defined by changes of the lid margin, meibomian gland dysfunction, redness of the eye, conjunctival chemosis and inflammation of the cornea. Differential diagnosis
Some more serious conditions can present with a red eye, such as infectious keratitis, angle-closure glaucoma, or iritis. These conditions require the urgent attention of an ophthalmologist.
Symptoms result from the release of histamine and other active substances by mast cells, and consist of redness (mainly due to vasodilation of the peripheral small blood vessels), swelling of the conjunctiva, itching, and increased production of tears. Bacterial
Bacterial conjunctivitis causes the rapid onset of conjunctival redness, swelling of the eyelid, and a sticky discharge. Typically, symptoms develop first in one eye, but may spread to the other eye within 2–5 days. Conjunctivitis due to common pus-producing bacteria causes marked grittiness or irritation and a stringy, opaque, greyish or yellowish discharge that may cause the lids to stick together, especially after sleep. Severe crusting of the infected eye and the surrounding skin may also occur. The gritty or scratchy feeling is sometimes localized enough that patients may insist that they have a foreign body in the eye.Common bacteria responsible for nonacute bacterial conjunctivitis are Staphylococcus, Streptococcus, and Haemophilus species. Less commonly, Chlamydia spp. may be the cause. Bacteria such as Chlamydia trachomatis or Moraxella spp. can cause a nonexudative but persistent conjunctivitis without much redness. Bacterial conjunctivitis may cause the production of membranes or pseudomembranes that cover the conjunctiva. Pseudomembranes consist of a combination of inflammatory cells and exudates and adhere loosely to the conjunctiva, while true membranes are more tightly adherent and cannot be easily peeled away. Cases of bacterial conjunctivitis that involve the production of membranes or pseudomembranes are associated with Neisseria gonorrhoeae, β-hemolytic streptococci, and Corynebacterium diphtheriae. C. diphtheriae causes membrane formation in conjunctiva of unimmunized children.