It has been observed that contact lens solution often evaporates overnight. The evaporation of contact lens solution occurs due to many underlying reasons. Keep in mind that contact lenses are inclined to suck up the contact lens solution when they are soaked in it. Contact lenses with higher water content tend to absorb the solution in larger quantity.
Climatic factors are the reason behind the evaporation. The partial evaporation of the disinfectant in the contact lens case unfortunately reduces the disinfecting ability of the contact lens solution. The preservative in the solution that works to disinfect contact lenses evaporate when the contact lens case is opened. Therefore; we can say that the evaporation of contact lens solution is actually the evaporation of the preservative that kills the bacteria. This explains that why one should not top off contact lens solution.
According to the research study by AMO that was conducted to judge the concentration of various branded disinfectants upon partial evaporation reveals that:
- ReNu with MoistureLoc (Bausch + Lomb) lost 75 to 99 percent of its ability to kill Fusarium fungi, 90 to 100 percent of its effectiveness against Candida fungi, and 29 to 33 percent of its effectiveness against Acanthamoeba microorganisms.
- Opti-Free Replenish (Alcon) lost 72 to 90 percent of its disinfecting efficacy against Fusarium and Candida fungi, and 10 to 61 percent of its effectiveness against Acanthamoeba.
- ReNuMultiPlus (Bausch + Lomb) lost 79 percent of its effectiveness against Candida fungi (when the solution was evaporated to four times its normal concentration).
- AQuify Multi-Purpose (Ciba Vision) lost 34.5 percent of its effectiveness against Candida fungi (4x concentration).
- Biotrue (Bausch + Lomb) lost 48 percent of its effectiveness against Candida fungi (4x concentration).
- Complete RevitaLens (Abbott Medical Optics) showed no loss in disinfecting effectiveness for the microorganisms tested.
Always keep the disinfectant bottle tightly capped and do not keep it open for long. Also do not touch the nozzle or tip of the solution bottle since the inoculation & evaporation both affect the concentration of the solution negatively. The study data proves that only AMO contact lens solution retains the efficacy even after partial evaporation.
The study was published online by Contact Lens & Anterior Eye (Journal of the British Contact Lens Association) on March 10, 2011.