A key risk factor and cause exposure for Acanthamoeba keratitis involves contact lens use with which exposure?

• A. Swimming in lakes or hot tubs
• B. Eating shellfish
• C. Dry eye using artificial tears
• D. Nighttime wearing contact lenses only

Answer: (A)

When people wear contact lenses, exposure to contaminated water is a major doorway for Acanthamoeba keratitis. Acanthamoeba are found in natural and inadequately treated water, and when lenses are worn while swimming or exposed to water (for example, swimming in lakes or hot tubs, or handling lenses with wet hands), organisms can adhere to the lenses and be carried to the cornea. This combination—lens wear plus water exposure—greatly increases the risk of infection and explains why swimming in lakes or hot tubs is the best answer. The other options don’t involve contact lens-associated water exposure, so they don’t fit as well.