Contact lens solution is designed to clean, disinfect, and safely store lenses. Like the lenses themselves, the solution has a strict shelf life. Using an expired product is a common oversight, but it carries specific health risks because the solution loses its potency.
Why Solution Efficacy Declines
Contact lens solution expires due to the chemical stability of its active ingredients. These solutions contain biocidal agents, such as polyquaternium-1 or polyhexamethylene biguanide, which naturally degrade over time. This decrease in concentration means the solution can no longer guarantee the elimination of harmful microorganisms.
Manufacturers assign a strict expiration date based on this loss of biocidal activity, even for unopened bottles. Once the seal is broken, the product’s sterility is compromised by environmental exposure and contaminants introduced during routine use. Preservative efficacy is only guaranteed for a limited time, often 90 days after opening, leaving lenses inadequately disinfected if used past that date.
Potential Eye Health Consequences
Using expired contact lens solution significantly increases the risk of developing microbial keratitis, an infection of the cornea. When biocidal agents fail, lenses become a vector for pathogens like bacteria, fungi, and protozoa. Bacterial keratitis can progress rapidly, causing inflammation, pain, and potentially permanent vision impairment if not treated quickly.
A severe risk is Acanthamoeba keratitis, a rare corneal infection caused by a resilient amoeba found in water and soil. An expired solution fails to neutralize this organism, allowing it to adhere to the lens surface and damage corneal tissue. This infection is difficult to treat and often requires a corneal transplant.
Expired solution can also cause immediate irritation and discomfort. Chemical breakdown alters the solution’s careful balance of pH and osmolarity, making it toxic to the corneal epithelium. This toxicity manifests as persistent redness, a burning sensation, and dryness, which compromises the eye’s natural barrier and increases susceptibility to secondary infections.
What to Do If You Used Expired Solution
If you realize you have used expired solution, immediately discard the remainder of the bottle. Do not use the old solution again, as its disinfecting power is unreliable. If you are unsure how long lenses were stored in the expired product, it is safest to dispose of them to eliminate microbial contamination.
If you choose to keep your lenses, clean and disinfect them using a brand-new, unexpired bottle of solution before placing them back in your eyes. This neutralizes any pathogens that may have colonized the lens surface. Even after taking corrective measures, closely monitor your eyes for any signs of trouble over the next several days.
When to Seek Professional Help
Certain symptoms warrant an immediate visit to an eye care professional, as they indicate a developing infection. These signs include:
- Persistent or worsening eye pain.
- Increased light sensitivity (photophobia).
- Blurred or decreased vision.
- Redness that does not improve.
Early detection of keratitis is paramount to a successful outcome and minimizing damage to the cornea.
To prevent this issue in the future, develop a habit of checking the expiration date on the bottle before use. Write the date you opened the new bottle on the label using a permanent marker, and discard the product 90 days later, regardless of how much solution remains.