Saline solution is a simple, sterile, and pH-balanced mixture of purified water and sodium chloride (common table salt). This composition, typically a 0.9% salt concentration, closely matches the natural salt level of human tears, making it gentle and compatible with the eye’s delicate surface. While saline is necessary for contact lens hygiene, its role is highly limited and it should not be confused with a comprehensive contact lens solution. You can and should use saline for contacts, but only for specific steps, as it lacks the chemical agents required for cleaning and disinfection.
The Specific Role of Saline in Contact Care
Saline solution is primarily intended as a final rinse for contact lenses before they are placed into the eye. After lenses have been thoroughly cleaned and disinfected, a quick rinse with saline removes any loosened debris or residual cleaning chemicals that could cause irritation. This final rinsing step improves comfort upon insertion.
In multi-step cleaning systems, particularly those involving hydrogen peroxide, saline is sometimes used to rinse lenses after cleaning but before disinfection. It also serves as the medium for dissolving protein-removal tablets used for deep cleaning deposits. Furthermore, certain saline solutions are packaged as rewetting or lubricating drops, which can be applied directly to the eye while wearing contacts to alleviate dryness.
Saline’s balanced composition ensures that it hydrates the lens without causing the lens material to swell or shrink, maintaining its intended fit and shape. Its simplicity is its strength, as it introduces no harsh chemicals or antimicrobial agents to the eye immediately before insertion. This function of simple hydration and rinsing is the extent of its approved use in a contact lens routine.
Why Saline Cannot Replace Disinfecting Solutions
The difference between saline and disinfecting solutions lies in their chemical composition and intended function. Saline is a simple saltwater mixture that is sterile when bottled but contains no preservatives or active antimicrobial agents. Once the bottle is opened and the lenses are introduced, the solution is immediately vulnerable to contamination.
If contacts are stored in plain saline, any bacteria, fungi, or protozoa present on the lens or in the case will not be killed; instead, they can multiply rapidly. This creates a high safety risk, as the lenses become a breeding ground for organisms that can cause serious eye infections, such as microbial keratitis. A particularly dangerous organism is Acanthamoeba, a free-living amoeba that can cause a devastating infection of the cornea.
Disinfecting solutions, by contrast, contain chemical compounds engineered to kill these pathogens. Using saline as a substitute for a disinfecting solution or for long-term storage leaves the eye exposed to an increased risk of infection. The purpose of disinfection is to sterilize the lens surface, a task that plain saline is chemically incapable of performing.
Essential Alternatives for Cleaning and Storage
Since saline is not a disinfectant, contact lens users must rely on dedicated solutions for cleaning and storage. The two primary types of effective lens care systems are Multipurpose Solutions and Hydrogen Peroxide Systems. Multipurpose solutions are the most common, offering the convenience of cleaning, rinsing, disinfecting, and storing lenses all in one bottle.
These solutions utilize a combination of ingredients, including surfactants to clean the lens surface and antimicrobial agents to kill germs. When using a multipurpose solution, the routine involves manually rubbing the lens with the solution to remove debris, followed by a soak period for disinfection. The convenience of this all-in-one approach makes it the most popular choice for many contact lens wearers.
Hydrogen Peroxide Systems offer a deep-cleaning alternative, often preferred by people with sensitive eyes because the final product is preservative-free. This system uses a 3% hydrogen peroxide solution to disinfect the lenses. The peroxide must be neutralized, typically by a built-in catalyst in the lens case or a separate neutralizing tablet, before the lenses can be worn. This neutralization process converts the peroxide into harmless saline and water, which prevents a painful chemical burn if the unneutralized solution contacts the eye.