Infectious conjunctivitis is inflammation of the conjunctiva usually caused by viruses or bacteria.
A variety of microorganisms may infect the conjunctiva (the membrane that lines the eyelid and covers the white of the eye). 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 the uninfected eye. Fungal infections are rare and occur mainly in people who use corticosteroid eye drops for a long time or have eye injuries involving organic matter, such as plants or dirt. Newborns are particularly susceptible to eye infections, which they acquire from organisms in the mother's birth canal (neonatal conjunctivitis—see Problems in Newborns: Some Infections of Newborns).
Inclusion conjunctivitis is a particularly long-lasting form of conjunctivitis caused by certain strains of the bacterium Chlamydia trachomatis. Inclusion conjunctivitis usually spreads by contact with genital secretions from a person who has a genital chlamydial infection. Trachoma (see Conjunctival and Scleral Disorders: Trachoma) is another type of conjunctivitis caused by Chlamydia trachomatis. Another type of conjunctivitis is caused by Neisseria gonorrhoeae (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 clear layer in front of the iris and pupil).
When infected, the conjunctiva becomes pink from dilated blood vessels, and a discharge appears in the eye. 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 blinked away. If the cornea is infected, vision also blurs but does not improve with blinking. Sometimes the eye feels irritated, and bright light may cause discomfort. Very rarely, severe infections that have scarred the conjunctiva lead to long-term vision difficulties.
Viral conjunctivitis differs from bacterial conjunctivitis in the following ways:
These factors, however, cannot always accurately differentiate viral conjunctivitis from bacterial conjunctivitis.
People with inclusion conjunctivitis or with conjunctivitis caused by 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 usually closely examined with a slit lamp (an instrument that enables a doctor to examine the eye under high magnification). Samples of infected secretions may be sent to a laboratory to identify the infecting organism by a culture. However, doctors usually send samples to a laboratory only in certain situations:
Prognosis and Treatment
Most people with infectious conjunctivitis eventually get better without treatment. However, some infections, particularly those caused by some bacteria, may last a long time if not treated. Inclusion conjunctivitis may persist for months if not treated.
If discharge accumulates on the eyelid, people should gently wash the eyelid (with the eye closed) with tap water and a clean washcloth. Warm or cool compresses sometimes soothe the feeling of irritation. Because infectious (bacterial or viral) conjunctivitis is highly contagious, people should wash their 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. In the most severe cases of viral conjunctivitis, people sometimes stay home for weeks.
Antibiotics are helpful only in bacterial conjunctivitis. However, because it is difficult to distinguish between bacterial and viral infections, doctors sometimes prescribe antibiotics for everyone with conjunctivitis. Antibiotic eye drops or ointments, such as moxifloxacin, ciprofloxacin, or trimethoprim/polymyxin, which are effective against many types of bacteria, are used for 7 to 10 days. Drops are usually effective, but ointments are sometimes used because they last longer. However, ointments can blur vision.
Inclusion conjunctivitis requires antibiotics, such as azithromycin, doxycycline, or erythromycin, 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. Antiviral eye drops are not helpful for most conjunctivitis caused by viruses, with some exceptions. For example, a person with viral conjunctivitis caused by herpes may apply antiviral drugs to the eyes (trifluridine eye drops) or take them by mouth (acyclovir).
Last full review/revision November 2012 by Melvin I. Roat, MD, FACS