Porth's Essentials of Pathophysiology, 4e

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Nervous System

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towels, etc., to the opposite eye or other persons. It may also be through contaminated eye drops. Depending on the cause, conjunctivitis can vary in severity from a mild hyperemia (redness) with tearing to severe conjunctivitis with purulent drainage. The conjunctiva is extremely sensitive to irritation and inflammation.Symptomsofconjunctivitisincludeaforeign body sensation, a scratching or burning sensation, itching, and photophobia or light sensitivity. Severe pain suggests corneal rather than conjunctival disease. A discharge, or exudate, may be present. It is usually watery when the conjunctivitis is caused by allergy, a foreign body, or viral infection, andmucopurulent (mucusmixedwithpus) in the presence of bacterial or fungal infection. Infectious forms of conjunctivitis are usually bilateral, whereas unilateral disease suggests sources of irritation such as foreign bodies. The diagnosis of conjunctivitis is based on history, physical examination, and microscopic and culture studies to identify the cause. Because a red eye may be the sign of several eye conditions, it is important to differentiate between redness caused by conjunctivitis, which affects peripheral conjunctival blood vessels (Fig. 38-4), and that caused by more serious eye disorders, such as corneal lesions and acute glaucoma, which affects blood vessels radiating around the edge of the cornea. Conjunctivitis also produces only mild discomfort compared with the moderate to severe discomfort associated with corneal lesions or the severe and deep pain associated with acute glaucoma. Viral Conjunctivitis. Adenoviruses are the most com- mon causes of viral conjunctivitis. 3 The infection, which is highly contagious, causes generalized conjunctival hyperemia, copious tearing, and minimal exudate, and is often accompanied by pharyngitis, fever, and malaise. Viral conjunctivitis usually spreads through direct contact with contaminated fingers, swimming pool water, or per- sonal items. Children are affected more often than adults. The disease usually lasts for at least 2 weeks and may be complicated by visual symptoms due to epithelial and subepithelial corneal involvement. There is no specific

treatment for this type of viral conjunctivitis. Preventive measures include hygienic measures and avoiding shared use of eyedroppers, eye makeup, goggles, and towels. Persons who use contact lenses should wear wearing them until the infection clears. Bacterial Conjunctivitis. Common agents of bacterial conjunctivitis are staphylococci, streptococci (particularly S. pneumoniae), Haemophilus species, Pseudomonas, and Moraxella. The infection usually is characterized by large amounts of yellow-green drainage. The eyelids are sticky, and there may be excoriation of the lid margins. Treatment measures include local application of antimi- crobial agents. The disorder usually is self-limited, lasting approximately 10 to 14 days if untreated and 1 to 3 days if properly treated. 3 Gonorrheal conjunctivitis, usually acquired through contact with genital secretions, is a severe, sight-threatening ocular infection. 3–5 The symptoms, include conjunctival redness and edema; lid swelling and tenderness; and swollen preauricular lymph nodes. Treatment includes systemic antimicrobial drugs supplemented with ocu- lar antimicrobials. Because of the increasing prevalence of penicillin-resistant N. gonorrhoeae, the choice of an antimicrobial agent should be determined by current information regarding antimicrobial sensitivity. Chlamydial, or inclusion, conjunctivitis, is usually a benign, suppurative conjunctivitis transmitted by the types of Chlamydia trachomatis (serotypes D through K) that causes venereal infections 3–6 (see Chapter 41). It is commonly spread by contact with genital secretions and occurs in newborns of mothers with C. trachomatis infections of the birth canal. 3–6 It is usually treated with appropriate oral antimicrobial agents. Trachoma, a more serious form of infection, is caused by a different strain of C. trachomatis (serotypes A, B, and C). 6 This form of chlamydial infection affects the conjunctiva and causes ulceration and scarring of the cornea. It is the leading cause of preventable blindness in the world, and is seen mostly in developing countries. 3,6 It is transmitted by direct human contact, contaminated objects (fomites), and flies. Allergic Conjunctivitis. Allergic conjunctivitis encom- passes a spectrum of conjunctival conditions usually characterized by itching. 3–5,7 The most common of these is seasonal allergic rhinoconjunctivitis, or hay fever. Seasonal allergic conjunctivitis is an immunoglobulin E (IgE)-mediated hypersensitivity reaction precipitated by small air-borne allergens such as pollens. 7 It typically causes bilateral tearing, itching, and redness of the eyes. The treatment of seasonal allergic rhinoconjunctivitis includes allergen avoidance and the use of cold compresses and eye washes with tear substitute. Allergic conjunctivitis also has been successfully treated with topical mast cell stabilizers, histamine type 1 (H 1 ) receptor antagonists, and topical nonsteroidal anti- inflammatory drugs. 7 Systemic antihistamines may be useful in prolonged allergic conjunctivitis. In severe cases, a short course of topical corticosteroids may be required to afford symptomatic relief.

FIGURE 38-4. Gonococcal conjunctivitis of right eye. Note injection (redness) of the peripheral conjunctival blood vessels. (From the Centers for Disease Control and Prevention Public Health Images Library. No. 6784.)