Now that cold & flu season is getting ready to start, the incidence of "pink eye" is starting to pick up. This is a very common condition that accounts for over 30 percent of doctor visits for eye problems.

Conjunctivitis is the medical term for "pink eye." The conjunctiva is the continuous connective tissue membrane that covers the inside of the eyelids. The membrane folds back onto itself to cover the front of the eyeball up to the edge of the cornea (where the white part of the eye meets the iris or colored part of the eye).

The purpose of the conjunctiva is to provide a barrier to keep infectious organisms from entering the eye tissue itself. Conjunctivitis results when there is an irritation or breakdown of this defensive layer, a change in the normal organisms living around the eye or trauma that breaches the membrane.

There are a number of causes of conjunctivitis. The most common are bacteria, viruses, allergies, fungi, parasites, and chemicals. These irritants cause varying degrees of redness, discharge, irritation and perhaps even pain on exposure to bright light (photophobia).

For doctors who do not have special equipment, it can sometimes be difficult to tell the exact cause of conjunctivitis. Ophthalmologists and optometrists have special equipment like slit lamps (the instrument that you rest your chin on when the eye doctor sweeps a bright light across your eye) that can help differentiate the cause.

Doctors without special equipment can sometimes get clues to the cause of the inflammation. For instance, people who have had a recent cold are more likely to have a viral cause. Viruses are also more common from early spring through late fall. Bacterial conjunctivitis is more common in the winter and spring. Patients may recall exposures to agents that might have led them to develop chemical or allergic conjunctivitis.

The symptoms of conjunctivitis can be quite variable. Most causes result in some type of eye discharge that results in matting of the eyes, particularly in the mornings when the eyelids may be stuck together. Patients may describe cloudy vision and an itching, burning or gritty feeling.

Bacterial conjunctivitis usually comes on fairly rapidly, has minimal pain and may have some associated itching. There is often thick discharge that may be yellow or green. Staph and Strep are the usual causative organisms. More serious bacterial organisms include Chlamydia and Neisseria gonorrhea. These latter two can lead to severe scarring and blindness, particularly in infants.

Viral conjunctivitis typically starts more slowly than bacterial forms and does not have much associated pain. The discharge is usually more watery with less matting. It may last a week or longer and is transmitted like the common cold - through sneezing, coughing, touching infected surfaces and also through contact with contaminated swimming pools.

Adenoviruses are the most common cause of viral conjunctivitis. Herpes viruses can cause very serious eye infections and may lead to scarring of the cornea and loss of vision.

Allergic conjunctivitis is also very common. The hallmark of this type of irritation is itching along with watery discharge and burning. There is usually a history of exposure to some known allergen.

Treatment for conjunctivitis depends on the cause. Most cases will resolve on their own with time without any lasting effects. Most people don't want to wait it out.

Since it is often difficult to tell whether the infectious agent is bacterial or viral, most doctors will choose to treat a presumed infection with antibiotic eye drops or ointment. Drops are nice since they don't interfere with vision. Ointments are more soothing and allow the medication to be in contact with the conjunctiva longer.

Local treatment with cool compresses can also be soothing. Most schools and daycares want children to be treated for at least 24 hours before they return.

Allergic conjunctivitis can be an ongoing problem as long as the offending agent is able to come into contact with the eye. The person should avoid the allergen if possible. Over the counter antihistamine eye drops and cool compresses can also be helpful.

There are steps you can take to help prevent conjunctivitis. Wash your hands or use hand sanitizer. Also, don't share eye drops or washcloths with people who have colds or eye infections.