When facing an unexpected situation without contact lens solution, the urgency to store lenses safely often leads people to consider household liquids. This is a high-risk scenario, as contact lenses are medical devices requiring a sterile, chemically balanced environment to prevent severe eye damage and infection. While a few temporary measures exist for emergencies, they should be used only as a last resort. The safest course of action is almost always to avoid reinserting any lens that has not been properly disinfected.
The Three Functions of Proper Contact Lens Solution
Commercial contact lens solutions are complex chemical formulas designed to perform multiple functions that keep the lens and the eye healthy. The primary role of these solutions is to eliminate harmful microorganisms that naturally accumulate on the lens surface during wear. The solution contains specific chemical disinfectants that break down the cell walls of bacteria, fungi, and protozoa, ensuring the lens is safe to place back onto the eye.
Another function is to maintain the correct osmotic balance and pH level, which is necessary for both the lens material and the health of the eye. Contact lens solution is formulated to match the precise conditions of healthy human tears (pH 7.4 and osmolarity of about 300 mOsm/L). Matching these conditions prevents discomfort or damage to the corneal cells.
The correct balance of salts and water also ensures the lens material retains its proper shape and flexibility. When lenses are exposed to liquids with different concentrations, they can swell or shrink, a phenomenon known as osmotic shock. Proper solutions also contain wetting agents and lubricants, which coat the lens to keep it hydrated and comfortable.
Liquids to Absolutely Avoid and Why
The most dangerous substitute for contact lens solution is ordinary tap water, which is not sterile and often harbors microorganisms. The most serious risk is exposure to Acanthamoeba, a free-living amoeba commonly found in tap water. This organism can cause Acanthamoeba keratitis, a rare, painful, and potentially sight-threatening corneal infection that is difficult to treat.
Beyond biological contaminants, tap water contains minerals like calcium and chlorine that can bind to the soft lens material. These deposits can cause chronic irritation, blurred vision, and lens spoilage. Tap water is also hypotonic, meaning it has a lower salt concentration than the eye, causing the lens to absorb water and tightly adhere to the cornea.
Bottled water and distilled water are also unsuitable, despite being purified. Distilled water is not guaranteed to be sterile for ophthalmic use and lacks the necessary salts and buffers to maintain the lens’s dimensional stability. Storing lenses in these liquids causes the lens to swell due to improper osmotic balance. This swelling changes the fit of the lens and can trap microorganisms against the eye.
Using saliva is another dangerous mistake because the mouth is home to a high concentration of bacteria. Saliva contains oral flora like Pseudomonas aeruginosa and other pathogens that are harmless in the mouth but can cause aggressive eye infections upon transfer. Enzymes in saliva can also degrade the lens material, making the lens surface rough and more prone to harboring bacteria.
Homemade saline solutions, created by mixing salt and water, must be avoided entirely. It is impossible to achieve the necessary sterile conditions and precise sodium chloride concentration in a home environment. The resulting non-sterile solution can introduce contaminants, including Acanthamoeba from the water source. Furthermore, the incorrect tonicity will cause the lens to warp or shrink.
Immediate Actions and Safe Alternatives for Short-Term Storage
If you have no disinfecting solution, the only safe liquid alternative for temporary hydration is commercially prepared, sterile saline solution. This solution will keep the lens moist and prevent it from drying out. However, saline does not contain any disinfecting agents. Lenses stored in saline must be properly disinfected immediately upon obtaining a multipurpose or hydrogen peroxide solution.
If no solution, including sterile saline, is available, the safest option is to remove the lenses and store them dry in a clean, empty case or container. High-cost or custom lenses can be stored this way for a very short period (less than 12 hours), but they will dry out and become brittle. For any lens that is not a daily disposable, the best recommendation is to discard it to prevent the risk of infection.
Before reinserting any lens that was stored dry or temporarily hydrated with saline, a follow-up protocol must be strictly followed.
Mandatory Disinfection Protocol
The lens must be cleaned by rubbing it with fresh multipurpose solution for the manufacturer’s recommended time, then rinsed thoroughly. The lens must then soak in a fresh, full change of disinfecting solution for a minimum of four to eight hours. If any redness, pain, blurred vision, or foreign body sensation occurs after reinsertion, the lens should be removed immediately and an eye care professional consulted.