Putting contact lenses in distilled water is definitively unsafe. Contact lens solution is an intricate, medically formulated substance designed to clean, disinfect, and store lenses in a safe environment, and water cannot substitute for it. Proper lens care is a serious component of maintaining eye health. Using any type of water, even distilled, introduces significant risks that can compromise both the lens and the eye. The complex chemistry of the eye and the lens material requires a specific, balanced solution to prevent physical damage and contamination.
The Chemical Problem: Why Water Damages Lenses and Cells
Distilled water causes a chemical reaction with the contact lens material that can physically damage the lens and irritate the cornea. Soft contact lenses are designed to exist in a balanced environment called an isotonic solution, which matches the natural salt concentration of tears. Distilled water is hypotonic, containing significantly fewer dissolved salts and electrolytes than lens solution. When a soft lens is placed in this environment, the process of osmosis causes the lens material to absorb water to balance the concentration gradient. This absorption causes the lens to swell, altering its shape and corrective power, making it fit improperly on the eye.
The swollen lens can lead to discomfort, blurred vision, or cause the lens to stick to the cornea, potentially leading to small abrasions when removed. This osmotic imbalance can also cause the corneal cells themselves to absorb water, a condition known as corneal edema, which further compromises eye health.
The Biological Danger: Infection Risk from Water
Beyond the physical damage, using distilled water poses a significant biological danger because it is not a sterile liquid. While the distillation process removes minerals and impurities, it does not guarantee the complete absence of microorganisms, especially once the seal is broken or if it is left standing. The lack of disinfecting agents in water means that any bacteria, fungi, or parasites present can rapidly multiply and colonize the lens surface and the storage case.
The most severe risk associated with exposing contact lenses to any water source is the parasite Acanthamoeba. This microscopic, free-living amoeba is commonly found in water and soil and can adhere to the contact lens and infect the cornea. The resulting infection, known as Acanthamoeba keratitis, is devastating, often causing extreme pain and being notoriously difficult to treat. Treatment sometimes requires months of intensive therapy or even a corneal transplant. Water also allows other common waterborne pathogens, such as the bacterium Pseudomonas aeruginosa, to flourish on the lens, leading to other forms of microbial keratitis.
Safe Solutions and Emergency Protocols
The only liquids safe for contact lens care are commercially produced, sterile solutions specifically designed for the purpose. These solutions fall into categories such as multipurpose solutions, which clean, rinse, and disinfect, and hydrogen peroxide-based systems, which provide deep cleaning and disinfection. Saline solution is another product, but it is only safe for rinsing the lens or temporary hydration, as it lacks the necessary disinfecting and cleaning agents.
Emergency Protocols
If you find yourself without the proper solution, the safest protocol is to remove the lenses and store them dry in a clean case until a sterile solution can be acquired. If the lenses must be kept moist for a short time, sterile saline solution or preservative-free artificial tears can be used as a temporary, non-disinfecting measure. Never attempt to create a homemade solution, as these lack the correct balance and sterility and pose the same contamination risks as water. Discarding the lenses and using a fresh pair once a proper solution is available is always the preferred choice to protect eye health.