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A 41-year-old man wakes up with eyes that are reddened bilaterally (Figure 27-1). He has some burning and itching in the eyes, but no pain. He describes minimal crusting on his eyelashes. Examination shows no loss of vision, no foreign bodies, and pupils that are equal, round, and reactive to light. He is diagnosed with viral conjunctivitis, which does not require antibiotic treatment. He is advised about methods to prevent spreading conjunctivitis to others and is asked to notify the physician immediately if he experiences eye pain or loss of vision. He recovers spontaneously without complications after a few days.


Bilateral viral conjunctivitis in a 41-year-old man. (Reproduced with permission from Richard P. Usatine, MD.)


A red eye signifies ocular inflammation. The differential diagnosis includes both benign and sight-threatening conditions. The pattern of redness; presence/absence of eye pain or photophobia, vision loss, or eye discharge; involvement of cornea; and visual acuity are helpful in differentiating among causes (see Table 27-1). Although most red eyes seen in the primary care setting are a result of viral conjunctivitis, several causes of red eye require urgent referral.

TABLE 27-1Clinical Features in the Diagnosis of Red Eye


  • An acute red eye or eyes is a common presentation in ambulatory and emergency departments.

  • Conjunctivitis is the most common cause of a nontraumatic red eye in primary ...

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