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Patient Story

A 4-year-old boy woke up with one eye matted shut. The child’s parents cleared the matted material with a warm washcloth and brought the child into the doctor’s office. The child indicates discomfort but not pain. The child and the parents believe the child’s vision is fine. On examination, the child is afebrile with conjunctival injection, lid swelling and purulent discharge in the left eye (Figure 12-1). Vision testing is normal. Based on the age of the child and the purulence of the discharge, bacterial conjunctivitis was diagnosed and antibiotic drops were prescribed.


Unilateral conjunctivitis in a 4-year-old child. The child’s age and purulent discharge are consistent with a bacterial etiology. (Used with permission from Richard P. Usatine, MD.)


Conjunctivitis, inflammation of the membrane lining the eyelids and globe, presents with injected pink or red eye(s), eye discharge ranging from mild to purulent, eye discomfort or gritty sensation, and no vision loss. Conjunctivitis is most commonly infectious (viral or bacterial) or allergic, but can be caused by irritants. Diagnosis is clinical, based on differences in symptoms and signs.


Pink eye.


  • Infectious conjunctivitis is common and often occurs in outbreaks, making the prevalence difficult to estimate.

  • In the US, the estimated annual incidence rate for bacterial conjunctivitis is 135 per 10,000 people, with 23 percent, 28 percent and 13 percent of cases occurring in children ages 0 to 2, 3 to 9, and 10 to 19, respectively.1

  • Viral conjunctivitis is far more common than bacterial conjunctivitis.

  • Allergic conjunctivitis in children and adults had a point prevalence of 6.4 percent and a lifetime prevalence of 40 percent in a large population study in the US from 1988 to 1994.2

Etiology and Pathophysiology

Conjunctivitis is predominately infectious (bacterial or viral) or allergic, and the most common etiologies vary by age.

  • Neonatal conjunctivitis is often caused by Chlamydia trachomatis and Neisseria gonorrhoeae.3

  • Children younger than 6 years are more likely to have a bacterial than viral conjunctivitis. In the US, the most common bacterial causes are Haemophilus species and Streptococcus pneumoniae accounting for almost 90 percent of cases in children.4,5

  • Children age 6 years or older are more likely to have viral or allergic causes for conjunctivitis.4 Adenovirus is the most common viral cause.


  • To distinguish conjunctivitis from other causes of a red eye, ask about pain and check for vision loss. Patients with a red eye and intense pain or vision loss that does not clear with blinking are unlikely to have conjunctivitis and should undergo further evaluation.

  • Always ...

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