Recognizing Eye Infections

Every day, patients seek treatment for eye infections, which have a variety of causes and can affect any part of the eye. Eye infections usually are treated aggressively, because seemingly benign infections can quickly become serious and threaten vision. Symptoms that indicate an eye infection include chronic redness, persistent pruritus, flaking of the eyelid, eye discomfort or pain, blurred vision, eye discharge, and edema of ocular tissue. The following disease descriptions and case vignettes highlight a variety of eye infections, both common and uncommon, with which patients may present.

Conjunctivitis
Worldwide, conjunctivitis is an extremely common eye condition that has a variety of causes, including bacterial, viral, fungal, parasitic, allergic, toxic, and chemical. It is typically a self-limited process but can progress to a severe, sight-threatening infection, depending on the patient's immune status and the cause.

Classic presentations generally involve eye discharge, pruritus, and a burning or gritty foreign-body sensation. Vision disturbances may be reported; however, this is more likely related to pus sliding across the eye than any actual declines in visual acuity.¹ Bilateral disease suggests an infectious or allergic cause, whereas unilateral disease is more indicative of a toxic, chemical, mechanical, or lacrimal cause. Acute cases of conjunctivitis most often have a bacterial or viral cause.

Bacterial conjunctivitis is characterized by acute onset, minimal pain, and occasional pruritus. Thick and purulent discharge is common and generally copious. Chemosis is typical. Staphylococcal and streptococcal species are most often the causative pathogens, although Neisseria species, Chlamydia trachomatis, and other bacteria have been associated with this infection (Figures 1 and 2). Neisserial conjunctivitis is considered an ocular emergency and is indicative of systemic disease.

Figure 1 – This patient's conjunctivitis was a consequence of Reiter syndrome-a triad of arthritis, conjunctivitis, and urinary tract infection or urethritis (A). The disease usually begins in a region of an existing bacterial infection, such as an infection caused by Chlamydia trachomatis. (Photograph courtesy of Joe Miller and the Centers for Disease Control and Prevention.)

Figure 2 – This image shows phlyctenular conjunctivitis in an 8-yearold child with a recent tuberculosis infection. The arrow points to a gray nodule (phlycten) on the lateral limbus of the pupil. (Photograph from Rennert W. Images of tuberculosis. Infect Med. 2006;23:604- 615.)

Viral conjunctivitis is characterized by acute or subacute onset, minimal pain, and exposure history. Pruritus and a clear, watery discharge are also common. Severe photophobia and foreign-body sensation sometime occurs. Adenovirus is usually the cause when the infection is associated with keratitis. If preauricular adenopathy and a follicular conjunctival change are present, the diagnosis is probably epidemic keratoconjunctivitis; however, herpes simplex virus and chlamydia can also cause these findings.