Contact lens wearers at greater risk for Acanthamoeba keratitis than non-lens wearers

Stephen C. Kaufman, MD, PhD

Acanthamoeba keratitis is a rare but significant ocular infection, which affects approximately five to 600 individuals in the U.S. per year and can result in severe pain, blindness and loss of the eye. The Centers for Disease Control and Prevention noted a sevenfold increase in the risk of developing Acanthamoeba keratitis in individuals who wear soft contact lenses, but amoebic keratitis may also affect non-contact lens users. Individuals who wear their soft contact lenses while swimming and showering are particularly susceptible to this type of infection. Acanthamoeba ocular infections are commonly associated with symptoms of pain, which may be out of proportion to the clinical appearance of the eye, redness, blurred vision, photophobia and tearing. Slit lamp examination initially reveals a nondescript keratitis with an irregular epithelium. What makes this infection difficult to diagnose is the finding of a keratitis that may resemble a keratitis associated with contact lens overwear or epithelial herpes simplex virus keratitis or microsporidia keratitis. Early diagnosis of the infection is important because the early, more superficial stage of the infection results in a greater diagnostic success rate with scraping, cultures and confocal microscopy, less morbidity and has a higher treatment success rate. As the infection progresses, a white intracorneal ring-infiltrate develops.
Unfortunately, there are no FDA approved medications for ocular Acanthamoeba keratitis; however, there are custom compounded medications, which include chlorhexidine, polyhexamethylene biguanide and others. When medical treatments are not successful, surgical intervention may be necessary and generally involves a penetrating keratoplasty. As always, prevention is preferable to treatment. Contact lens care should always include the avoidance of nonsterile water contact with contact lenses; this includes tap water, shower water, swimming pools, lakes, sea water and hot tubs. Do not overwear contact lenses and replace contact lenses as scheduled. Wash hands with soap and dry the hands before handling contact lenses. Clean contact lenses according to instructions, never top off solutions or use homemade cleaning or storage solutions and never mix solutions with tap water. The contact lens storage cases should also be cleaned regularly, replaced on a regular basis and always air dry the case between uses. Contact lens are a great benefit to many patients, but they require proper care.