Eye Care - Acanthamoeba
Acanthamoeba keratitis is a rare but very painful and potentially blinding infection of the cornea, the transparent covering at the front of the eye. The infection rate is approximately one in 30,000 contact lens wearers and in around 85% of cases the condition is associated with contact lens use.
The organism that causes the infection, Acanthamoeba, has been found in virtually every environment, including soil, dust, fresh water and seawater. Acanthamoeba is also found in chlorinated swimming pools, hot tubs, domestic tap water and even in bottled water. It is also present, without causing infection, in the nasal passages of healthy people.
Risk factors for infection in contact lens wearers are:
· Use of tap water during lens care (to rinse lenses or the storage case)
· Wearing lenses while swimming (without goggles), showering or in hot tubs
· Use of ineffective lens care solutions
· Failure to follow lens care instructions
Many contact lens users ignore the advice of their contact lens practitioner and lens care instructions and rinse their lenses or storage case in tap water, which may introduce Acanthamoeba to the storage case. Once inside the case, Acanthamoeba can survive and grow, feeding on bacteria that may also contaminate the case. Organisms are then transferred from the case to the cornea on the contact lens. The lens holds the organisms in place on the eye, which may ultimately lead to infection.
The use of contact lenses while in contact with water sources that may be contaminated - ie swimming in fresh, salt or chlorinated water, water sports, showering and use of hot tubs – is also a risk factor for Acanthamoeba keratitis. The infecting organisms can reach the eye directly from the water source, or indirectly by introduction of Acanthamoeba into the storage case when a lens contaminated by the water source is not cleaned properly.
Symptoms of Acanthamoeba keratitis include a sensation of having something in the eye, watery eyes, blurred vision, sensitivity to light, swelling of the upper eyelid and extreme pain. If the disease is recognised early, when only the surface layer of the cornea is infected, it may respond rapidly to treatment. However, if the disease is recognised late then intensive treatment may be needed for up to 12 months. Infection can also reoccur after treatment.
Most cases of Acanthamoeba keratitis are preventable if contact lens wearers follow the instructions given to them by their contact lens practitioner and on their lens care products. Contact lens wearers not complying with these instructions may be increasing their risk of infection with Acanthamoeba and other organisms. Not all contact lens solutions have the same disinfecting ability, so changing solutions without the advice of your contact lens practitioner is not recommended.
Guidelines for the prevention of Acanthamoeba keratitis are:
· Always use the lens care system prescribed to you by your contact lens practitioner
· Wash and thoroughly dry your hands prior to applying, removing and cleaning your contact lenses
· Dispose of the disinfecting solution when lenses are removed for wear
· Air-dry the storage case and keep dry when lenses are being worn
· Fill the storage case with fresh disinfecting solution when lenses are stored after use
· Never use tap water to store or wash lenses or cases – only sterile solutions should be used
· Replace your lens storage case monthly to prevent a build-up of contamination
· Remove lenses prior to showering, swimming, water sports, hot tub use etc
· If lenses must be worn when swimming, wear goggles and disinfect lenses afterwards.
Source: BCLA