Acanthamoeba and contact lenses

Importance guidance to minimise the risk of infection

Never allow water to come into contact with your contact lenses or contact lens storage case.

Never rinse your lenses in tap water as it contains many impurities that can contaminate or damage your lenses and may lead to serious eye infection and vision loss. 

If you feel that your contact lenses or your contact lens case may have been contaminated with water then replace them with new ones immediately.

Problems with contact lenses are thankfully rare but research shows that they are more likely to occur if the recommended hygiene procedures are not followed1. That's why it's important to listen carefully to the advice of your contact lens practitioner and always follow their instructions on lens wear and care – as well as those of the contact lens manufacturer.

What is Acanthamoeba keratitis?

One type of infection affecting the cornea, the transparent front part of the eye, is Acanthamoeba keratitis, a rare but very painful condition that can cause sight loss.

In the United States, an estimated 85 per cent of cases occur in contact lens users. The incidence of the disease in developed countries is approximately one to 33 cases per million contact lens wearers2.

The organism that causes the infection, Acanthamoeba, has been found in almost all environments, including soil, dust, fresh water and seawater. Acanthamoeba is 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 include:

• Using tap water during lens care (to rinse lenses or the storage case)
• Wearing lenses while swimming (without goggles), showering or in hot tubs
• Using ineffective lens care solutions
• Failing to follow lens care instructions

Symptoms

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 you experience any of these symptoms, remove your contact lenses and consult your contact lens practitioner immediately, who will advise you what to do next.

If the infection is recognised early, when only the surface layer of the cornea is affected, it may respond rapidly to treatment. However, if the infection is recognised later 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.

References

1. Hickson-Curran, S, Chalmers, R, Riley, C, 'Patients' attitudes and behavior regarding hygiene and replacement of soft contact lenses and storage cases.' Contact Lens & Anterior Eye. 2011 Oct; 34 (5): 207-15.

2. Centres for Disease Control (USA) http://www.cdc.gov/parasites/acanthamoeba/epi.html