Exposing contact lenses to water from any source, including tap water, showers, swimming pools, or distilled water, is strongly advised against. Water is chemically incompatible with the lens material and is not sterile, creating two distinct hazards. The immediate danger involves a physical change to the lens itself, altering its fit and comfort. The more significant risk is biological, introducing various microorganisms that can cause severe eye infections.
Physical Changes to the Contact Lens
Soft contact lenses are hydrogel materials designed to maintain a precise shape and water content, balanced against the salt concentration of tears and commercial solutions. This balance relies on osmolarity, the concentration of dissolved particles in a fluid. Contact lens solutions are formulated to be isotonic, matching the osmolarity of the eye’s natural environment.
Most water sources, such as tap water, are hypotonic, meaning they have a lower salt concentration than the lens material. When submerged, the soft lens acts like a sponge and rapidly absorbs the surrounding fluid through osmosis. This influx of water causes the hydrogel structure to swell and change its curvature and diameter.
The swollen lens will no longer fit correctly on the cornea, which can lead to discomfort, blurred vision, or a foreign object sensation. A lens that adheres too tightly can cause tiny abrasions on the eye’s surface. These microscopic tears compromise the eye’s natural protective barrier, making it vulnerable to infection.
The Threat of Microbial Contamination
The most serious consequence of exposing contact lenses to water is the introduction of microorganisms present in non-sterile environments. Water contains bacteria, fungi, and protozoa that can be devastating to the delicate surface of the eye. Even treated tap water, which is potable for drinking, contains organisms that standard water filtration does not eliminate.
One concerning pathogen is Acanthamoeba, a microscopic organism commonly found in soil and various water sources, including tap water and swimming pools. Exposure can lead to Acanthamoeba keratitis, a rare but sight-threatening corneal infection. This protozoan is resilient because it can enter a dormant, cyst form that resists typical disinfection methods and the body’s immune system.
When a contact lens touches water, Acanthamoeba can adhere to the lens surface. The lens acts as a vector, trapping the pathogen directly against the cornea. The tight fit and the presence of micro-abrasions from a swollen lens create a favorable environment for the organism to penetrate the corneal tissue and cause infection. Other waterborne bacteria, such as Pseudomonas aeruginosa, can also adhere to a contaminated lens, leading to rapid and painful corneal ulcers that require immediate medical intervention.
Immediate Steps After Water Exposure and Safe Storage
If a contact lens has been exposed to water—whether from a shower, a splash, or accidental storage—it must be removed from the eye immediately. Daily disposable lenses must be discarded without any attempt to clean or reuse them. For reusable lenses, the safest course of action is also to discard them to eliminate the risk of infection completely.
If discarding is not possible, reusable lenses should be thoroughly disinfected using a fresh, FDA-approved multipurpose or hydrogen peroxide solution for the entire recommended soaking time. Rinsing the lens with tap water, bottled water, or saline solution will not disinfect it. If the eye was exposed to water while wearing the lens, monitor it for symptoms of infection, including persistent redness, pain, increased light sensitivity, or blurred vision.
Proper contact lens care requires the exclusive use of commercially manufactured lens solutions designed for cleaning, rinsing, and storage. These solutions are formulated to be sterile and isotonic, maintaining lens integrity while containing disinfectants. Contact lens cases should only be cleaned with fresh solution, never water, and should be allowed to air-dry open after each use to prevent pathogen growth.