Saline solution is a simple mixture of sodium chloride (salt) and sterile water, widely used in medicine because it mimics the body’s natural fluids. This isotonic quality means the solution has a salt concentration of approximately 0.9%, matching the osmotic pressure of human tears. Saline is excellent for rinsing and irrigation, but its safety for the eye depends entirely on how the product was prepared. You must check the label to confirm the solution is manufactured specifically for ophthalmic use, as non-sterile or improperly formulated products can cause serious damage to the delicate ocular surface.
Identifying Ophthalmic-Grade Saline
Saline products considered safe for the eye are known as ophthalmic-grade solutions, which include sterile eye washes and contact lens rinsing solutions. These products are manufactured under strict conditions to ensure they are completely free of bacteria, foreign particles, and contaminants. The packaging must be sealed at the factory to maintain this high level of sterility until the product is opened for use.
The characteristic that makes these solutions comfortable is their isotonicity, meaning they contain the same concentration of dissolved particles as your natural tears. A 0.9% sodium chloride concentration is the ideal formulation, which prevents the painful swelling or shrinking of corneal cells. While the eye can tolerate a small range of tonicity, specifically from approximately 0.6% to 1.8% sodium chloride equivalency, solutions outside this range will cause noticeable discomfort.
Many ophthalmic solutions are also buffered to closely match the eye’s natural pH of about 7.4. This careful pH adjustment is done to prevent the stinging or burning sensation that can result from using a solution that is too acidic or too alkaline. When purchasing a product, look specifically for terms like “sterile eye wash,” “ophthalmic solution,” or “rinsing solution for sensitive eyes” to ensure it meets these medical standards.
Saline Solutions That Pose a Risk
Several common types of saline should never be used in the eyes because they lack necessary sterility or contain harmful additives. Homemade saline solutions are unsafe because it is nearly impossible to guarantee the sterility of the water or the container. Using non-sterile solutions introduces a high risk of infection, including parasitic infections such as Acanthamoeba keratitis, which can be difficult to treat and may lead to vision loss.
Nasal saline sprays and sinus rinses also pose a significant risk, even if they are sterile. These products are often formulated with a higher salt concentration, sometimes up to 3%, making them hypertonic. This higher concentration is designed to draw water out of nasal tissues, but in the eye, it causes severe irritation and cellular dehydration.
Non-ophthalmic solutions, such as wound wash or irrigation saline, may contain preservatives like benzyl alcohol, which is toxic to the sensitive cells on the eye’s surface. While these products may be labeled as “normal saline” or 0.9% sodium chloride, their manufacturing standards are not regulated for the delicate environment of the eye. The bottles are often non-sterile once opened, making them inappropriate for ocular application.
Safe Application and When to Seek Medical Help
When using an approved ophthalmic saline product, first wash your hands thoroughly with soap and water to minimize the transfer of bacteria. The bottle tip should never touch the eye, eyelid, or any other surface, as this will immediately contaminate the solution and risk infection. To apply, tilt your head back, hold the dropper or bottle tip over the eye, and squeeze the solution into the lower eyelid area while looking up.
Saline is intended for flushing minor irritants like dust, sand, or pollen from the eye. You should blink frequently during the rinse to help wash the particles out completely. If you experience persistent pain, redness, or a change in vision after flushing, or if a foreign object seems embedded in the eye, stop using the saline and seek medical attention immediately. For chemical exposure, you must begin flushing the eye continuously with water or sterile saline for at least 20 minutes while simultaneously arranging for emergency medical care.