Atlas of pathophysiology, 2 Edition

Part II - Disorders

Sensory Disorders

Conjunctivitis

Conjunctivitis is characterized by hyperemia of the conjunctiva. The three main types of conjunctivitis are infectious (called pinkeye), allergic, and chemical. This disorder usually occurs as benign, self-limiting pinkeye; it may also be chronic, possibly indicating degenerative changes or damage from repeated acute attacks. Epidemic keratoconjunctivitis is an acute, highly contagious viral conjunctivitis. Careful hand washing is essential to prevent the spread of conjunctivitis.

Causes

Infectious conjunctivitis

Most commonly by:

·   Bacterial—Staphylococcus aureus, Streptococcus pneumoniae, Neisseria gonorrhoeae, Neisseria meningitidis

·   Chlamydial—Chlamydia trachomatis (inclusion conjunctivitis)

·   Viral—adenovirus types 3, 7, and 8; herpes simplex 1

Allergic conjunctivitis

Hypersensitivity to:

·   Pollen, grass, unknown seasonal allergens (vernal conjunctivitis), animals

·   Topical medications, cosmetics, fabrics

·   Air pollutants, smoke

·   Contact lenses or solutions

Chemical conjunctivitis

Chemical reaction to:

·   Environmental irritants (wind, dust, smoke, swimming pool chlorine)

·   Occupational irritants (acids, alkalies)

Pathophysiology

Conjunctivitis is an inflammation of the conjunctiva, the transparent layer covering the surfaces in the inner eyelid and the front of the eyeball. It usually begins in one eye and rapidly spreads to the other by contamination of towels, washcloths, or the patient's own hands.

Vernal conjunctivitis (so called because symptoms tend to be worse in the spring) is a severe form of immunoglobulin E–mediated mast cell hypersensitivity reaction. This form of conjunctivitis is bilateral. It usually begins between ages 3 and 5 and persists for about 10 years. It's sometimes associated with other signs of allergy commonly related to pollens, asthma, or allergic rhinitis.

Signs and symptoms

·   Hyperemia of the conjunctiva

·   Discharge, tearing

·   Pain, photophobia

Acute bacterial conjunctivitis (pinkeye)

·   Usually lasts only 2 weeks

·   Itching, burning, and the sensation of a foreign body in the eye

·   Crust of sticky, mucopurulent discharge on the eyelids

N. gonorrhoeae conjunctivitis

·   Itching, burning, foreign body sensation

·   Profuse, purulent discharge

Viral conjunctivitis

·   Copious tearing, minimal exudate

·   Enlargement of the preauricular lymph node

·   In children, sore throat or fever if the cause is an adenovirus

·   Variable time course, depending on the virus:

§  some self-limiting, lasting 2 to 3 weeks

§  others chronic, producing a severe disabling disease

Diagnostic test results

·   In stained smears of conjunctival scrapings, the predominance of lymphocytes indicates viral infection; of neutrophils, bacterial infection; of eosinophils, allergy-related infection.

·   Culture and sensitivity tests identify the causative organism.

Treatment

·   Bacterial conjunctivitis: topical appropriate broad-spectrum antibiotic

·   Viral conjunctivitis:

§  resists treatment; most important aspect of treatment is preventing transmission

§  herpes simplex infection generally responsive to treatment with trifluridine drops, vidarabine ointment, oral acyclovir

§  secondary infection possibly prevented by sulfonamide or broad-spectrum antibiotic eyedrops

·   Vernal (allergic) conjunctivitis:

§  corticosteroid drops followed by cromolyn sodium

§  cold compresses to relieve itching

§  occasionally, oral antihistamines

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CLINICAL MANIFESTATIONS OF CONJUNCTIVITIS

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