The difference between contact lens solution and saline solution is a common source of confusion for contact lens wearers. While both liquids play a part in lens hygiene, they are not interchangeable, and confusing their roles can compromise eye health. Understanding the specific composition and intended function of each solution is necessary for maintaining lens safety and comfort. This article clarifies the distinct purposes of these two products and the health implications of using one in place of the other.
Why Contact Solution Is Not a Saline Substitute
Contact solution is not a suitable substitute for saline because their chemical compositions are fundamentally different. Saline solution is a simple, pH-balanced mixture of purified water and sodium chloride, which mimics the natural salt concentration in tears and is intended only for rinsing. Contact solutions, such as multipurpose or cleaning solutions, are complex formulas designed to actively clean and disinfect lenses.
These complex formulations contain active ingredients like surfactants, which break down protein and lipid deposits that build up on the lens surface. They also include disinfecting agents and preservatives intended to kill microbes, such as bacteria and fungi. These compounds are potent enough to be effective cleansers, but they are not meant for continuous, direct application to the eye surface. The cleaning agents and preservatives can be irritating or toxic to the cornea and conjunctiva if not rinsed away or neutralized before lens insertion.
Repeatedly introducing these active chemicals directly into the eye by using contact solution as a routine final rinse can lead to conditions like chemical conjunctivitis or corneal irritation. Hydrogen peroxide-based systems are particularly strong and must be neutralized over several hours in a special case before the lenses can be safely worn. Using an un-neutralized hydrogen peroxide solution directly as a rinse would cause immediate burning, redness, and potential damage to the eye’s surface.
Functional Roles of Saline and Multipurpose Solutions
The distinct ingredients in each product dictate its specific function within the lens care routine. The primary function of saline solution is purely for rinsing the lens surface before insertion or for rehydrating the lens. It acts as a neutral medium to wash away debris or loosened deposits without introducing harsh chemicals, ensuring the lens is comfortable and clear when it touches the eye. Saline does not possess significant cleaning or germ-killing properties, meaning it cannot be used to disinfect or store lenses.
Conversely, the role of a contact solution, especially a multipurpose formula, is to perform multiple functions beyond simple rinsing. Its job is disinfection, actively killing harmful pathogens that accumulate on the lens during wear. It also performs cleaning by chemically breaking down and removing organic matter like proteins and lipids. In many modern routines, a multipurpose solution handles the entire process of cleaning, disinfecting, and storing the lenses, making a separate saline rinse unnecessary for many users.
Protecting Eye Health Through Proper Usage
Misapplication of contact lens solutions can have clear physiological consequences, making adherence to proper usage instructions necessary for eye health. Using contact solution repeatedly as a saline rinse exposes the eye to a higher concentration of preservatives and cleaning agents than intended, increasing the risk of toxic buildup. This overexposure can manifest as corneal irritation, where the surface of the eye becomes inflamed, leading to discomfort, redness, and a gritty sensation. Over time, this chemical irritation can contribute to chronic dry eye symptoms or contact lens-related papillary conjunctivitis, an inflammatory condition of the inner eyelid.
To maintain eye health, always use a dedicated, commercially prepared sterile saline solution solely for rinsing, if a rinse is part of your prescribed regimen. Contact solution should only be used for the active cleaning, disinfection, and storage of the lenses, as directed by the manufacturer.
Never attempt to substitute sterile saline or contact solution with non-sterile liquids like tap water. Tap water contains microorganisms, including the parasite Acanthamoeba, that can cause severe, sight-threatening infections. Following the manufacturer’s and eye care professional’s instructions for each specific product is the safest way to ensure both lens performance and ocular comfort.