Monday, May 22, 2017

Brief Summary of Conjunctivitis

Hyperemia of the conjunctiva from infection, allergy, or chemical reactions characterizes conjunctivitis. Bacterial and viral conjunctivitis are highly contagious but are also self-limiting after 2 weeks. Chronic conjunctivitis may result in degenerative changes to the eyelids. In the Western hemisphere, conjunctivitis is probably the most common eye disorder.

The most common causative organisms are the following:
  • bacterial: Staphylococcus aureus, Streptococcus pneumoniae, Neisseria gonorrhoeae, Neisseria meningitidis
  • chlamydial: Chlamydia trachomatis (inclusion conjunctivitis)
  • viral: adenovirus types 3, 7, and 8; herpes simplex virus type 1.
Other causes include allergic reactions to pollen, grass, topical medications, air pollutants, and smoke; occupational irritants (acids and alkalies); rickettsial diseases (Rocky Mountain spotted fever); parasitic diseases caused by Phthirus pubis and Schistosoma haematobium; and, rarely, fungal infections.

Vernal conjunctivitis (also called seasonal or warm-weather conjunctivitis) results from allergy to an unidentified allergen. This form of conjunctivitis is bilateral; it usually begins before puberty and persists for about 10 years. Sometimes it’s associated with other signs and symptoms of allergy commonly related to grass or pollen sensitivity.
An idiopathic form of conjunctivitis may be associated with certain systemic diseases, such as erythema multiforme, chronic follicular conjunctivitis (orphan’s conjunctivitis), thyroid disease, and Stevens-Johnson syndrome. Conjunctivitis may be secondary to pneumococcal dacryocystitis or canaliculitis from candidal infection.

Clinical Features

Conjunctivitis commonly produces hyperemia of the conjunctiva, sometimes accompanied by discharge and tearing. It generally doesn’t affect vision unless there is corneal involvement, which also causes pain and photophobia. Conjunctivitis usually begins in one eye and rapidly spreads to the other by contamination of towels and washcloths or by the patient’s own hands.

Acute bacterial form
With acute bacterial conjunctivitis (pinkeye), the infection usually lasts only 2 weeks. The patient typically complains of itching, burning, and the sensation of a foreign body in his eye. The eyelids show a crust of sticky, mucopurulent discharge. If the disorder stems from N. gonorrhoeae, however, the patient exhibits a profuse, purulent discharge.

Viral form

Viral conjunctivitis produces copious tearing with minimal exudate and enlargement of the preauricular lymph node. Some viruses follow a chronic course and produce severe disabling disease; others last 2 to 3 weeks.

Physical examination reveals injection of the bulbar conjunctival vessels. In children, systemic signs and symptoms may include sore throat and fever.
Monocytes are predominant in stained smears of conjunctival scrapings if conjunctivitis is caused by a virus. Polymorphonuclear cells (neutrophils) predominate if conjunctivitis stems from bacteria; eosinophils, if it’s allergy related. Culture and sensitivity tests help identify the causative bacterial organism and indicate appropriate antibiotic therapy.

The cause of conjunctivitis dictates the treatment. 

Bacterial conjunctivitis requires topical application of the appropriate antibiotic or sulfonamide. If the causative agent is N. gonorrhoeae, a single I.M. dose of ceftriaxone is usually given. If the cornea is involved, a 5-day I.M. course is required.
Although viral conjunctivitis resists treatment, broad-spectrum antibiotic eyedrops may prevent secondary infection.
Herpes simplex infection generally responds to treatment with trifluridine drops, vidarabine ointment, or oral acyclovir, but the infection may persist for 2 to 3 weeks. 

Treatment of vernal (allergic) conjunctivitis includes administration of corticosteroid drops followed by lodoxamide tromethamine, a histamine 1 antagonist, cold compresses to relieve itching and, occasionally, an oral antihistamine.
Instillation of a one-time dose of erythromycin into the eyes of newborns prevents gonococcal and chlamydial conjunctivitis.

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