Chapter 18: Conjunctivitis

PATIENT STORY

A 35-year-old woman presents with 2 days of redness and tearing in her eyes (Figure 18-1). She has some thin matter in eyes, but neither eye has been glued shut when she awakens. She does not have any trouble seeing once she blinks to clear any accumulated debris. Both eyes are uncomfortable and itchy, but she is not having any severe pain. She does not wear contact lenses and has not had this problem previously. The patient was diagnosed with viral conjunctivitis and scored –1 on the clinical scoring system (see "Diagnosis" below). She was instructed about eye hygiene and recovered in 3 days.

INTRODUCTION

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.

SYNONYMS

Pink eye.

EPIDEMIOLOGY

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

• In the United States:

  • The estimated annual incidence rate for conjunctivitis is 22,000 per 1 million people per year¹

  • Viral conjunctivitis is more common than bacterial conjunctivitis

  • Allergic conjunctivitis had a point prevalence of 6.4% and a lifetime prevalence of 40% in a large population study in the United States from 1988 to 1994²

  • The direct healthcare costs related to conjunctivitis are estimated to be $800 million per year.¹

• Worldwide, Chlamydia trachomatis is a common cause of conjunctivitis in adults and newborns. In 2016, almost 2 million people worldwide lost their eyesight to chlamydial eye infections.³ Blindness due to chlamydial infection is rare in the United States because of neonatal prophylactic treatment programs.

ETIOLOGY AND PATHOPHYSIOLOGY

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

• Neonatal conjunctivitis is often caused by C. trachomatis and Neisseria gonorrhoeae.⁴

• Children younger than 6 years are more likely to have a bacterial than viral conjunctivitis (Figure 18-2). In the United States, the most common bacterial causes are Haemophilus species and Streptococcus pneumoniae accounting for almost 90% of cases in children.⁵

• Children age 6 years or older are more likely to have viral or allergic causes for conjunctivitis.⁵ Adenovirus is the most common viral cause.