When a contact lens wearer runs out of disinfecting solution, using water to store lenses overnight can seem like a simple fix. However, the answer to whether you can safely store contact lenses in water is “No.” Contact lenses require a specific, sterile environment to maintain their integrity and protect the health of your eyes. Using water, even briefly, introduces significant risks that proper contact lens solution is designed to prevent.
Why Tap Water Poses an Infection Risk
Tap water, bottled water, and even distilled water are not sterile environments suitable for contact lens storage. These sources contain microorganisms, including bacteria and fungi, that can adhere to the lens material and be transferred directly to the eye. Disinfecting solutions are specially formulated with antimicrobial agents to kill these pathogens, a function water lacks.
The most concerning microbial risk is the presence of Acanthamoeba, a microscopic organism commonly found in tap water. If this amoeba becomes trapped between the lens and the cornea, it causes a severe eye infection called Acanthamoeba keratitis. This infection is painful, difficult to treat, and can lead to permanent vision loss or blindness.
Storing lenses in tap water is directly linked to Acanthamoeba keratitis. Rinsing a lens case with water can introduce this microbe, which thrives in the moist environment. Exposure to water bypasses the disinfection step, risking the hygiene of the lenses and the health of the eye.
How Water Physically Damages Contact Lenses
Beyond the microbial threat, storing lenses in water causes physical damage to the lens material. Contact lenses, especially soft lenses, are designed to be isotonic, meaning their salt and solute concentration matches the eye’s natural tear film. This balance is maintained by the storage solution.
Water is hypotonic, meaning it has a lower salt concentration than the lens material. When a soft contact lens is submerged, it acts like a sponge and absorbs water through osmosis. This absorption causes the lens to swell, altering its curvature and shape.
A warped lens fits poorly on the eye, leading to discomfort, irritation, and potential corneal abrasion upon reinsertion. A damaged corneal surface provides an easy entry point for remaining microbes, compounding the infection risk. Tap water also contains minerals that bind to the porous lens material, creating deposits that reduce clarity and irritate the eye.
Safe Emergency Alternatives
If you find yourself without multipurpose disinfecting solution, the safest option is to wear your backup glasses and discard the exposed lenses. If you cannot discard the lenses, obtain an approved, sterile contact lens disinfecting solution immediately.
Sterile saline solution may be used temporarily to keep lenses hydrated. However, saline does not contain disinfecting agents and will not kill harmful bacteria or amoebae. Lenses stored in saline must be thoroughly cleaned and disinfected with a proper multipurpose solution before they are worn again. Never use homemade saline, saliva, or any other unapproved liquid, as these can introduce severe pathogens.