Saline solution and contact lens solution are not the same products and serve fundamentally different functions in the care of reusable contact lenses. The core difference lies in their chemical composition and intended use, with one designed for rinsing and the other for comprehensive cleaning and disinfection. Recognizing this distinction is important for maintaining the longevity of your lenses and the health of your eyes. Understanding the proper use of each solution prevents misuse that can lead to serious eye complications.
The Simple Purpose of Saline Solution
Saline solution is a simple, sterilized preparation of purified water and sodium chloride (common table salt). This formulation is balanced to be isotonic, meaning its salt concentration matches the natural salinity of human tears (typically around 0.9%). This physiological compatibility makes it gentle on the delicate tissues of the eye.
The sole purpose of saline is to rinse contact lenses, removing loosened debris or residual cleaning agents after disinfection. It is also used to temporarily wet lenses before insertion to increase comfort. Because it lacks active antimicrobial or cleaning components, saline solution cannot clean, disinfect, or store lenses for any extended period. It acts only as a final rinse or hydration step.
The Complex Role of Multipurpose Solutions
Modern multipurpose contact lens solutions (MPS) are complex formulations designed to perform several tasks at once, earning them the name “all-in-one.” These solutions must clean, disinfect, rinse, and store soft contact lenses. The ingredients are chosen to be effective against microorganisms while remaining compatible with the eye and the lens material.
A primary component is a surfactant, a cleaning agent that works to loosen and lift deposits such as proteins, lipids, and environmental debris from the lens surface. The solution also contains antimicrobial or disinfecting agents, such as polyquaternium or polyaminopropyl biguanide, which kill bacteria, fungi, and other pathogens that cause eye infections. Buffering agents are included to maintain the solution’s pH level, ensuring comfort and optimizing disinfectant function.
The combination of these components allows a single solution to perform the full hygiene cycle required for reusable lenses. When a lens is soaked in MPS, the disinfecting agents sterilize the lens, while the conditioning agents hydrate and prepare the lens for comfortable wear. This comprehensive function is why MPS is the product required for daily lens storage and disinfection.
The Consequences of Misusing These Products
The most significant danger comes from substituting saline solution for a true multipurpose or disinfecting solution for lens storage. Since saline contains no antimicrobial agents, storing lenses in it allows bacteria, fungi, and other pathogens to rapidly multiply on the lens surface. This pathogen accumulation significantly increases the risk of serious ocular infections, such as microbial keratitis, which can threaten vision.
Conversely, using a multipurpose solution too liberally for rinsing the eye or as a rewetting drop can also cause discomfort. The disinfectants and preservatives necessary to keep the solution sterile can cause irritation, redness, or a stinging sensation if applied directly to the eye’s surface. Even though the solution is safe for the lens, some individuals can develop an allergic or toxic reaction to these chemical components, leading to ocular irritation.
Following the specific instructions from your eye care professional and the product manufacturer is the most important safety guidance. If a lens care product does not come with a new lens case, it may indicate that it is only a rinsing agent and not a disinfecting solution. Always use the correct solution for cleaning and storing your lenses.