Running out of contact lens solution often leads people to look for a quick, household alternative, such as tap water, to store or rinse their lenses. However, using any type of water—including tap, bottled, or distilled—is dangerous for both your contact lenses and your eye health. Commercial solutions are designed to eliminate the significant risks associated with this practice.
Why Tap Water Damages Contact Lenses and Eyes
The danger of using water stems from two main scientific problems: the presence of microorganisms and an osmotic imbalance. Tap water, while safe for drinking, is not sterile and harbors microscopic organisms, including a free-living amoeba called Acanthamoeba. When contact lenses are soaked or rinsed in water, these organisms can attach to the lens surface, which then transfers the microbe directly to the cornea.
This can lead to an eye infection known as Acanthamoeba keratitis. This infection is difficult to treat and may result in permanent vision loss or the need for a corneal transplant. The risk is elevated because the soft contact lens material can trap the amoeba against the delicate corneal tissue for extended periods.
The second major issue involves the physical integrity of the soft contact lens. Contact lens solutions are balanced to be isotonic, meaning they have a salt concentration similar to natural tears. Water is hypotonic, lacking the necessary salts and buffering agents. When a lens is placed in hypotonic water, it absorbs the water due to osmosis, causing it to swell and change shape. This alteration can make the lens fit improperly, leading to discomfort, blurry vision, and potentially causing micro-abrasions on the cornea when reinserted.
Safe Steps for Handling a Solution Shortage
If you find yourself without contact lens solution, the safest course of action is to remove your lenses immediately and put on your glasses. If you wear daily disposable lenses, the best approach is to discard them entirely, as they are not meant to be stored or reused. For reusable lenses, storing them dry in a clean case is preferable to storing them in any type of water.
If you must keep the lenses moist for a few hours until you can acquire proper solution, the only acceptable temporary measure is sterile, unexpired saline solution. Saline is a simple salt-and-water mixture that can keep the lens hydrated without causing osmotic damage. However, saline only rinses and hydrates; it contains no disinfecting agents and will not kill bacteria or other pathogens.
Upon obtaining proper multipurpose or hydrogen peroxide solution, you must disinfect the lenses by soaking them for the manufacturer’s recommended time before reinserting them. You should never attempt to create a homemade saline solution, use household liquids like saliva, or any form of tap or bottled water. These prohibited substitutes lack the necessary sterility and chemical balance, posing a significant threat of infection or eye irritation.
The Specialized Role of Contact Lens Fluids
Commercial contact lens solutions are designed to perform multiple functions simultaneously that water cannot replicate. Multipurpose solutions contain specific chemical disinfectants, often polyquaternium-1 or similar agents, which kill bacteria, fungi, and protozoa. This disinfecting capability is the primary function that protects the eye from serious infections.
Solutions also contain surfactants, which act like gentle detergents to lift and wash away tear components like proteins, lipids, and calcium deposits from the lens surface. If these deposits are not removed, they can reduce lens clarity and cause chronic irritation to the eye. The inclusion of wetting agents ensures the lens remains lubricated and comfortable throughout the wearing period, acting as a buffer between the lens and the cornea.
Finally, lens fluids are pH-buffered to match the slightly alkaline environment of the eye, which prevents stinging and maintains the structural integrity of the lens material. This careful balancing of components ensures the solution is both effective at cleaning and gentle enough for contact with the sensitive eye surface. This complex chemical environment is why a purpose-made solution is the only safe product for lens care.