Leaving contact lenses in water overnight is a dangerous practice that you must avoid. The simple answer is “No.” Water, including tap water, distilled water, and bottled water, is not a sterile environment for contact lenses and should never be used for storage. Using water exposes your eyes to health risks from microscopic organisms and causes physical damage to the lens material itself.
Microbiological Dangers of Water Storage
Tap water, which is safe for drinking, is not sterile and contains microscopic life forms that pose a threat to your eyes. The most concerning is Acanthamoeba, a free-living amoeba commonly found in water sources globally. When a contact lens is soaked in water, this organism adheres to the lens surface, transferring the amoeba directly to the eye’s cornea.
This transfer can result in a rare but painful and sight-threatening infection called Acanthamoeba keratitis. The infection is difficult to treat because the amoeba can form a protective cyst that resists many common disinfectants. Treatment often requires specialized medication over several months, and in severe cases, the infection can cause permanent visual impairment or necessitate a corneal transplant. Proper contact lens solutions are formulated to kill these organisms, a function water cannot perform.
How Water Affects Contact Lens Material
Beyond the risk of infection, soaking lenses in water causes physical and chemical damage to the lens material. Contact lenses are designed to be stored in an isotonic solution, meaning it has a salt balance (osmotic pressure) similar to that of natural tears. Tap water is a hypotonic solution, possessing a much lower salt concentration than the lens.
This difference causes the lens material to absorb water through osmosis. As the lens absorbs this excess water, it swells, causing it to warp and change shape. A warped lens will not fit correctly, leading to discomfort, irritation, and potentially blurred vision when reinserted. Water also contains minerals like calcium, magnesium, and trace amounts of chlorine. These inorganic materials bind to the porous surface of the contact lens, forming deposits. Over time, these mineral deposits compromise the lens clarity and can scratch the delicate surface of the cornea.
Choosing and Using Proper Contact Lens Solutions
You should only store your lenses in a sterile, commercial disinfecting solution recommended by your eye care professional. Multipurpose solutions are the most common type, serving to clean, rinse, disinfect, and store the lenses in a single product. Hydrogen peroxide systems offer a deeper clean and disinfection, but they require a special case and a neutralization process before the lenses can be worn.
Saline solution is only suitable for rinsing the lenses and is not a substitute for a disinfecting solution, as it contains no germ-killing agents. If you lack disinfecting solution, the safest emergency option is to remove the lenses and store them dry in a clean, airtight container. You must then thoroughly clean and disinfect the lenses with a proper solution before wearing them again, or simply discard them.
Maintaining a clean lens case is just as important as using the correct solution. Always empty the old solution completely after each use, rub the inside of the case with clean fingers, and rinse it with fresh disinfecting solution. Never use water for this step. Leave the case open and air-dry it upside down on a clean tissue to prevent microbial growth between storage cycles.