Conjunctivitis : Overview, Causes, & Risk Factors

Alternate Names : Inflammation – conjunctiva, Pink eye

Definition

Conjunctivitis is swelling (inflammation) or infection of the membrane lining the eyelids (conjunctiva).

Overview, Causes, & Risk Factors

The conjunctiva is exposed to bacteria and other irritants. Tears help protect the conjunctiva by washing away bacteria. Tears also contain enzymes and antibodies that kill bacteria.

There are many causes of conjunctivitis. Viruses are the most common cause. Other causes include:

  • Allergies (allergic conjunctivitis)
  • Bacteria
  • Certain diseases
  • Chemical exposure
  • Chlamydia
  • Fungi
  • Parasites (rarely)
  • Use of contact lenses (especially extended-wear lenses)

“Pink eye” refers to a viral infection of the conjunctiva. These infections are especially contagious among children.

Newborns can be infected by bacteria in the birth canal. This condition is called ophthalmia neonatorum, and it must be treated immediately to preserve eyesight.

See also:

  • Allergic conjunctivitis
  • Keratoconjunctivitis sicca
  • Neonatal conjunctivitis
  • Trachoma
  • Vernal conjunctivitis

Pictures & Images

Eye

The eye is the organ of sight, a nearly spherical hollow globe filled with fluids (humors). The outer layer or tunic (sclera, or white, and cornea) is fibrous and protective. The middle tunic layer (choroid, ciliary body and the iris) is vascular. The innermost layer (the retina) is nervous or sensory. The fluids in the eye are divided by the lens into the vitreous humor (behind the lens) and the aqueous humor (in front of the lens). The lens itself is flexible and suspended by ligaments which allow it to change shape to focus light on the retina, which is composed of sensory neurons.


Review Date : 11/10/2008
Reviewed By : Linda Vorvick, MD, Family Physician, Seattle Site Coordinator, Lecturer, Pathophysiology, MEDEX Northwest Division of Physician Assistant Studies, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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