Infectious Conjunctivitis
Infectious conjunctivitis is inflammation of the conjunctiva caused by viruses, bacteria, or fungi.
A variety of microorganisms may infect the conjunctiva. The most common organisms are viral, particularly those from the group known as adenoviruses. Bacterial infections are less frequent. Both viral and bacterial conjunctivitis are quite contagious, easily passing from one person to another, or from a person's infected eye to his uninfected eye. Fungal infections are rare and occur mainly in people who use corticosteroid eye drops for a long time and in eye injuries involving vegetable matter. Newborns are particularly susceptible to eye infections, which they acquire from organisms in the mother's birth canal (neonatal conjunctivitis (see Section 23, Chapter 264)).
Inclusion conjunctivitis is a particularly long-lasting form of conjunctivitis caused by certain strains of the bacterium Chlamydia trachomatis. Inclusion conjunctivitis spreads by contact with genital secretions from a person who has a genital chlamydial infection. Another type of conjunctivitis is caused by Neisseria gonorrhea (gonorrhea), a sexually transmitted disease that also may spread to the eye.
Severe infections may scar the conjunctiva, causing abnormalities in the tear film. Sometimes, severe conjunctival infections spread to the cornea, the transparent part of the eye.
Symptoms and Diagnosis
When infected, the eye sometimes feels irritated, and bright light may cause discomfort. The conjunctiva becomes pink from dilated blood vessels, and a discharge appears in the eye. The discharge tends to be watery in viral conjunctivitis and thicker white or yellow in bacterial infection, but this distinction is not absolute. Often the discharge causes the person's eyes to stick shut, particularly overnight. This discharge may also cause the vision to blur; vision improves when the discharge is washed away. If the cornea is infected, vision also blurs but does not improve with washing. Very rarely, severe infections that have scarred the conjunctiva lead to long-term vision difficulties.
People with inclusion conjunctivitis or with conjunctivitis from gonorrhea often have symptoms of a genital infection, such as penile or vaginal discharge and burning during urination.
Doctors diagnose infectious conjunctivitis by its symptoms and appearance. The eye is closely examined with a slit lamp, an instrument that magnifies the surface of the eye. The slit lamp allows the doctor to see inflammation of the conjunctiva or infection of the cornea and front part of the eye (anterior chamber).
It is difficult to distinguish viral from bacterial conjunctivitis by appearance, although the presence of an upper respiratory infection increases the likelihood of a viral cause. Upper respiratory infections often accompany conjunctivitis caused by viruses, but they are rare in bacterial conjunctivitis. Samples of infected secretions may be sent to a laboratory to identify the infecting organism by a culture. However, doctors usually do this when the symptoms are severe or recurrent or when Chlamydia or N. gonorrhea is thought to be the cause.
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Prognosis and Treatment
Most people with infectious conjunctivitis eventually get better on their own. However, some infections, particularly those caused by some bacteria, may last a long time if not treated. Inclusion conjunctivitis persists for months.
People with conjunctivitis should gently wash the eyelid with tap water and a clean washcloth to keep it clean and free of discharge. Cool compresses sometimes soothe the feeling of irritation. Because infective (bacterial or viral) conjunctivitis is highly contagious, a person should wash his hands before and after cleaning the eye or applying drugs. Also, a person should be careful not to touch the infected eye and then touch the other eye. Towels and washcloths used to clean the eye should be kept separate from other towels and washcloths. People with infectious conjunctivitis generally stay home from work or school for a few days, just as they would with a cold.
Antibiotics are helpful only in bacterial conjunctivitis. However, because it is difficult to distinguish between bacterial and viral infection, doctors often prescribe antibiotics for everyone with conjunctivitis. Antibiotic eye drops or ointments, such as sulfacetamide or trimethoprim-polymyxin, that are effective against many types of bacteria are used for 7 to 10 days. Eye drops must be applied every 2 to 3 hours, because the drug is washed away by tears. Ointments last longer and are applied every 6 hours but blur vision.
Inclusion conjunctivitis requires antibiotics, such as erythromycin, azithromycin, or doxycycline, which are taken by mouth. Gonococcal conjunctivitis may be treated with an injection of ceftriaxone. Corticosteroid eye drops may be needed in some people with severe adenoviral conjunctivitis, particularly in those in whom inflammation of the eye is interfering with important daily activities. In a person with viral conjunctivitis caused by herpes, antiviral drugs may be applied to the eyes (trifluridine or idoxuridine eye drops or vidarabine ointment) or given by mouth (acyclovir). Antiviral drugs are not useful for infections caused by other viruses.
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