Pink Eye (Conjunctivitis)
Pink Eye (Conjunctivitis)
Pink eye refers to a chemical-or allergy-related inflammation, or a viral or bacterial infection, of the transparent covering of the eyelid and a portion of the eyeball. The transparent covering is called the conjunctiva, and so the inflammation or infection is known as conjunctivitis.
The designation pink eye indicates the appearance of the inflamed or infected conjunctiva, due to the increased prominence of blood vessels, which changes the color of the white portion of the eye to red or pink.
Infection-related conjunctivitis can be caused by viruses or bacteria. The microbes that are responsible are those that cause colds, ear infections, sore throats, and sexually transmitted diseases. Bacteria include Staphylococcus, Streptococcus, Chlamydia, Gonorrhea, and Hemophilus. Viruses include adenoviruses, rhinoviruses, coronaviruses, echoviruses, para-myxoviruses, and coxsackieviruses. Viral conjunctivitis is more common than the bacterial infections.
Infants can be infected during birth by bacteria in the mother's birth canal. While harmless in the mother, the bacteria are capable of causing an infection in the infant, whose immune system is not yet operating at full efficiency. The bacteria are described as being opportunitistic pathogens—they normally cause no harm, but can cause disease given the appropriate circumstances. Screening of the mother prior to the birth can detect and treat the infection. Newborn conjunctivitis is treated by the application of an antibiotic ointment to the eyes soon after birth.
The redness of the affected eye(s) is a hallmark of pink eye. Another common symptom is the feeling that something foreign is in the eye. Many people also complain of a gritty or itchy sensation in the infected eye(s). Other symptoms include blurred vision, increased sensitivity to light, increased formation of tears, and a discharge from the infected eye(s) that can become crusty during sleep.
Conjunctivitis can also be caused by an allergic reaction to pollen or some other substance. A part of the allergic response is the production of an antibody called immunoglobulin E, which in turn triggers cells in the eyes and airway to release various compounds. One of these compounds, histamine, produces a variety of allergic responses including allergic conjunctivitis.
WORDS TO KNOW
ANTIBIOTIC: A drug, such as penicillin, used to fight infections caused by bacteria. Antibiotics act only on bacteria and are not effective against viruses.
EYE DROPS: Eye drops are saline-containing fluid that is added to the eye to cleanse the eye or as the solution used to administer antibiotics or other medication.
HISTAMINE: Histamine is a hormone that is chemically similar to the hormones serotonine, epinephrine, and norepinephrine. A hormone is generally defined as a chemical produced by a certain cell or tissue that causes a specific biological change or activity to occur in another cell or tissue located elsewhere in the body. Specifically, histamine plays a role in localized immune responses and in allergic reactions.
OPPORTUNISTIC INFECTION: An opportunistic infection is so named because it occurs in people whose immune systems are diminished or are not functioning normally; such infections are opportunistic insofar as the infectious agents take advantage of their hosts’ compromised immune systems and invade to cause disease.
OPTIC SOLUTION: Any liquid solution of a medication that can be applied directly to the eye is an optic solution.
While the allergic response cannot be passed from person to person, viral and bacterial conjunctivitis are highly contagious.
Pink eye is global in occurrence and can affect anyone. Pink eye, like most minor contagious infections, spreads easily among groups of children. Viral and bacterial pink eye often affect children who live in group settings or attend school or day care.
People who develop bacterial or viral pink eye should avoid close contact with others. This is especially important for infants in day care and school-age children.
The cause of pink eye can be determined. If caused by a bacterial infection, pink eye is easily treated using antibiotics. Typically, the antibiotic is applied as an eye-drop solution, although an ointment can be used for infants and younger children. The infection usually clears up within several days. Even so, the antibiotic needs to be used for as long as has been prescribed to make sure all the infecting bacteria are killed. If treatment is stopped too early, some bacteria may survive and develop resistance to the antibiotic, making treatment of the recurring infection more difficult.
Allergic pink eye can be treated by use of eyedrops containing compounds that lessen symptoms. Rubbing the eye should be avoided, as it can introduce allergens and trigger more symptoms.
Good personal hygiene, especially handwashing and minimizing rubbing of the eyes, reduces the risk of developing pink eye. Frequently washing of bathroom and bedroom linens and avoiding sharing pillows and cosmetic applicators further lessen the risk of conjunctivitis.
While conjunctivitis is usually an inconvenience rather than a health concern, there is a risk that it can lead to problems with the cornea of the eye. As well, the infection in newborns can led to more serious health issues, including loss of vision. Prompt treatment can eliminate this concern.
In the United Kingdom, researchers and public health officials are currently studying the costs and benefits of changing common medical approaches to the treatment of viral and bacterial conjunctivitis. Since many cases of pink eye can disappear without medical intervention, researchers are developing new protocols for when parents should seek medical attention for children with conjunctivitis and how physicians should treat conjunctivitis. Public health officials have noted that antibiotic eyedrops are frequently prescribed, even before a clinical diagnosis of bacterial pink eye can be made. Use of antibiotics does not treat viral pink eye and only negligibly reduces recovery time for most cases of bacterial pink eye. Researchers worry that overzealous prescription of antibiotics could lead to bacterial resistance. Health officials note that patients’ costs associated with treating many mild forms of pink eye—including eyedrops, antibiotics, missed work, missed school, and doctors’ visits—may be unnecessarily high.
CONJUNCTIVA AND TEARS
A fine mucus membrane, the conjunctiva, covers the cornea and also lines the eyelid. Blinking lubricates the cornea with tears, providing the moisture necessary for its health. The cornea's out-side surface is protected by a thin film of tears produced in the lacrimal glands located in the lateral part of the orbit below the eyebrow. Tears flow through ducts from this gland to the eyelid and eye, and they drain from the inner corner of the eye into the nasal cavity. A clear watery liquid, the aqueous humor, separates the cornea from the iris and lens. The cornea contains no blood vessels or pigment and gets its nutrients from the aqueous humor.
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Weizer, Jennifer S., and Sharon Fekrat. All about Your Eyes. Raleigh: Duke University Press, 2006.