Contact lens solution is a sterile liquid necessary because lenses sit directly on the eye’s surface, collecting debris and microorganisms throughout the day. Proper maintenance prevents these contaminants from causing eye irritation or severe infections. The solution ensures lenses remain clean, disinfected, and hydrated, protecting the overall health of the eye.
The Essential Roles of Lens Solution
Contact lens solutions perform three functions: cleaning, disinfecting, and hydrating the lens material. Cleaning relies on surfactants, specialized molecules that act similarly to soap. These molecules lift and dissolve proteins, lipids, and other debris from the lens surface.
Disinfection is carried out by chemical agents that eliminate harmful microorganisms like bacteria and fungi. Many multi-purpose solutions use biguanides such as polyhexamethylene biguanide (PHMB) or polyquaternium-1 (Polyquad) to disrupt the cell membranes of pathogens. Hydrogen peroxide systems rely on the oxidative power of 3% hydrogen peroxide to generate hydroxyl free radicals, destroying microbial components.
The third role is maintaining the lens’s physical state and compatibility with the eye. Buffering agents, often citrates or borates, regulate the solution’s pH to keep it close to that of natural tears (ideally between 7.0 and 7.4). Wetting agents, such as hyaluronic acid or poloxamer, help the lens material attract and retain moisture, ensuring the lens remains soft and comfortable to wear.
Understanding Different Solution Types
Multi-Purpose Solution (MPS) combines cleaning, rinsing, disinfecting, and storage into a single bottle. While convenient, its chemical preservatives can occasionally lead to sensitivity or allergic reactions in some users. These reactions manifest as chronic redness or discomfort, sometimes requiring a switch to a preservative-free system.
Hydrogen Peroxide Systems offer a preservative-free alternative that provides robust disinfection, even against resilient microbes like Acanthamoeba. This system requires a specific case containing a neutralizing component, typically a platinum-coated disc or a catalytic tablet. This component breaks down the 3% hydrogen peroxide into a harmless saline solution over six to eight hours.
The neutralization process must be completed before the lens is placed in the eye. Inserting a lens soaked in un-neutralized peroxide will cause an immediate, intense burning sensation and a painful chemical burn to the cornea. Saline solution is a simple salt-and-water rinse that is isotonic with the eye. It is suitable only for rinsing the lens before insertion and should never be used for cleaning or long-term storage because it contains no disinfectants.
Best Practices for Solution Use and Storage
Always wash and dry hands thoroughly before handling lenses or solutions. The lens case is a common source of contamination and must be managed carefully. After placing lenses in the eye, the old solution should be dumped out, the case rinsed with fresh solution, and then allowed to air-dry upside down with the caps off.
Replace the contact lens case entirely at least every three months, as a bacterial film (biofilm) can form inside that is difficult to remove. Avoid “topping off,” which means adding new solution to the liquid already in the case. This practice dilutes the disinfectant, allowing microorganisms to thrive, and is a significant risk factor for infection.
Never substitute specialized solution with tap water, saliva, or homemade mixtures. Tap water contains the microscopic organism Acanthamoeba, which can cause a rare but sight-threatening infection called Acanthamoeba keratitis. Because solution potency decreases over time, users must adhere to the expiration date printed on the bottle and discard the solution within 30 to 90 days after opening.