I recently had a patient develop a red eye (keratoconjunctivitis) following swimming. What are the usual—and unusual—pathogen concerns?
 
“Red eyes are some of the most commonly encountered clinical entities, and have one of the broadest differential diagnosis sets in the field,” says Aaron Bronner, OD, a staff optometrist at the Pacific Cataract and Laser Institute of Kennewick, Wash.

In such cases, a well-taken history is instrumental in creating a manageable differential diagnosis, which should then guide the clinical exam.

“The majority of red eyes that develop after swimming are a result of either a toxic response to chlorine or other chemicals in the water, or an infection likely secondary to adenovirus,” says Blair Lonsberry, OD, MS, MEd, clinic director and professor of optometry at the Pacific University College of Optometry in Portland, Ore.

As such, reasonable differential diagnoses for a patient presenting with keratoconjunctivitis following swimming include chemical keratoconjunctivitis related to pool disinfectants or adenovirus conjunctivitis (pharyngoconjunctival fever [PCF]). Additionally, Acanthamoeba is another concern—particularly for contact lens wearers.

Red eyes that are a result of the chemical disinfectants found in pools will “typically have conjunctival injection and possible desiccation of the corneal epithelium, but won’t exhibit any specific findings” that indicate toxic keratopathy, says Dr. Bronner. Additionally, the onset of symptoms strongly correlates with the time of swimming.

Dr. Bronner suggests treatments such as preservative-free artificial tears, cold compresses as needed and, in some cases, a topical nonsteroidal agent for pain. Additionally, he recommends that contact lens wearers discontinue lens use.

Cases of swimming pool-borne, adenovirus-linked outbreaks of conjunctivitis have also been reported. These cases are most often PCF, and are commonly caused by adenovirus subtypes 3, 4 and 7. Clinical findings to support a PCF diagnosis include bilateral follicles, membranes or pseudomembranes. PCF may also lead to subepithelial infiltrates.

“PCF, as the name implies, doesn’t occur in an ocular vacuum, however,” says Dr. Bronner. Typically, patients who present with PCF will also develop a fever and an upper respiratory infection. Additionally, there is usually a delay of several days between the episode of swimming and the onset of symptoms, “so the history of a swimming pool red eye may not be as prominently described” he says.

“The last culprit to keep in mind while dealing with a swimming pool-related red eye is the biggie: Acanthamoeba keratitis (AK),” says Dr. Bronner. Contact lens wearers are most at risk for AK. In fact, according to Dr. Lonsberry, “85% to 95% of Acanthamoeba corneal infections are associated with contact lens wear, and of particular concern is contact lens wear in swimming pools and hot tubs.”_¹

Most cases of AK are unilateral. Because clinical findings early in the course of the disease are nonspecific, the condition is “often misdiagnosed as herpetic,” says Dr. Bronner. He adds that later stage stromal findings include the classic perineuritis and ring infiltrate—though these developments will not occur until several weeks into the disease course.

What further separates AK from other swimming pool-related red eyes is the clinical course; chemical keratoconjunctivitis should typically dissipate over the course of about one week, while AK will continue to worsen. “Therefore, any case of unilateral keratitis that does not behave as expected should have AK on the differential diagnosis list,” says Dr. Bronner.
A majority of red eyes that patients develop after swimming—if they are truly an infection and not a toxic response to pool disinfectants—are secondary to adenovirus exposure. “However,” Dr. Lonsberry cautions, “the clinician should be aware that there are potentially other causes that could have significantly more devastating consequences to the patient,” such as Acanthamoeba. He adds that contact lens wearers should be monitored closely; if their red eye worsens, it is necessary to rule out other potential infectious agents.

1. Stapleton F, et al. Contact lens-related Acanthamoeba keratitis. Optom Vis Sci. 2009;86(10):E1196-201.