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  1. What is the most common cause of conjunctivitis?

  2. What is the greatest risk factor for development of keratitis?

  3. Which symptom is most helpful for differentiating conjunctivitis from keratitis?

  4. Which infection is associated with unsterilized tap water?

  5. What is the most likely diagnosis in the patient with a recurrent history of a red eye?

  6. What are the three most common ways in which patients develop endophthalmitis?

Many eye infections are managed by the ophthalmologist, who possesses the specialized equipment and skills required for optimal diagnosis and treatment. However, infectious disease consultants and primary care physicians need to be familiar with these forms of infection to be able to initiate preliminary empiric therapy pending referral.



Usually responds rapidly to therapy and does not threaten vision.

Predisposing Factors

The conjunctiva is a mucous membrane that covers the globe of the eye up to the cornea and the lid of the eye. The surface of this transparent membrane is normally protected from infection by tears, which contain numerous antibacterial agents, including lysozyme and immunoglobulins A and G. Patients with decreased tear production—for example, those with scleroderma with infiltration of the lacrimal duct—often experience recurrent conjunctivitis and also keratitis.

Causes and Clinical Manifestations

Inflammation of the conjunctiva is called conjunctivitis. It is accompanied by dilatation of vessels within the membrane, causing the underlying white sclera to appear red. In addition to redness, pus formation accompanies conjunctivitis. Purulent discharge is commonly associated with swelling of the eyelids, pain, and itching. Upon awakening in the morning, the patient may find that dried exudate has glued the eyelid shut. Vision is usually unimpaired, and the cornea and pupil appear normal.

Bacteria, viruses, Chlamydia, fungi, and parasites can all cause conjunctivitis (Table 5-1). Allergic reactions and toxic substances can also produce inflammation of the conjunctiva. The specific findings on eye examination vary depending on the particular cause:

  1. Bacterial. Bacterial infection is more common in children and is highly contagious, particularly among children. Copious quantities of pus usually exude from the eye, and when pus is removed, it is quickly replaced by new exudate. The discharge is usually thick and globular.

  2. Viral. Viral infection is the most common cause of conjunctivitis in adults. The exudate in viral infection is less purulent and more serous in nature. In viral, chlamydial, and toxic conjunctivitis, the lymphatic tissue in the conjunctiva can become hypertrophied, forming small, smooth bumps called follicles. Viral conjunctivitis is highly contagious; the second eye commonly becomes involved within 24–48 hours. Unilateral involvement does not exclude the diagnosis, however. The infection is self-limiting, resolving over a period of 1–3 weeks.

  3. Chlamydial. Chlamydia trachomatis conjunctivitis is a leading cause of blindness worldwide. In the United States, this infection is most ...

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