Definition
Conjunctivitis is inflammation of the conjunctiva or thin membrane covering the white of the eye and the inner surface of the eyelid. The inflamed conjunctiva will usually make the eye appear red or pink because the tiny blood vessels that are normally within the conjunctiva are now irritated and enlarged.
The white of the eye (sclera) is covered by a thin, filmy membrane called the conjunctiva which produces mucus to coat and lubricate the surface of the eye. It normally has fine blood vessels within it, which can be seen on close inspection. When the conjunctiva becomes irritated or inflamed, the blood vessels which supply it enlarge and become much more prominent, and the eye turns red.
What Causes Conjunctivitis?
There are many different sources of eye irritation that can cause conjunctivitis. Bacterial infections can cause a red eye which is associated with a pus or discharge from the eye, or they can cause a red eye which is associated with crusting of the eyelashes with little or no discharge.
Viruses can cause conjunctivitis, such as the familiar red eyes, sore throat, and runny nose of a common cold. Viral conjunctivitis usually produces a watery discharge and lasts from one to two weeks. Infectious conjunctivitis, commonly known as "pink eye," can be quite contagious. Cloth handkerchiefs and towels should not be shared during this time. Handwashing will also help prevent the spread of this infection.
Allergies can also cause a conjunctivitis which produces a discharge. Allergies, like hay fever, can make the eyes itchy. Other allergies may only produce a chronic red eye. Environmental irritants such as smoke or fumes may cause conjunctivitis. Any type of conjunctivitis is aggravated by dryness of the eyes.
Symptoms
  • Pinkness or redness in the eye
  • Inflamed inner eyelids
  • Blurred vision
  • Sandy or scratchy feeling in the eye
  • Pus or watery discharge from the eye
The symptoms described above may not necessarily mean that you have conjunctivitis. However, if you experience one or more of these symptoms, contact your eye doctor for a complete exam.

Treatment
If you think you might have conjunctivitis, you should
  • Keep your hands away from your eyes;
  • Thoroughly wash hands before and after applying eye medications;
  • Do not share towels, washcloths, cosmetics or eyedrops with others;
  • Seek treatment promptly.
  • Small children, who may forget these precautions, should be kept away from school, camp and the swimming pool until the condition is cured.

Infectious conjunctivitis, caused by bacteria, is usually treated with antibiotic eye drops and/or ointment. Other infectious forms, caused by viruses, can't be treated with antibiotics. They must be fought off by your body's immune system. But some antibiotics may be prescribed to prevent secondary bacterial infections from developing. When treating allergic and chemical forms of conjunctivitis, the cause of the allergy or irritation must first be removed. For instance, avoid contact with any animal if it causes an allergic reaction. Wear swimming goggles if chlorinated water irritates your eyes. In cases where these measures won't work, prescription and over-the-counter eye drops are available to help relieve the discomfort.