Partially Evaporated Contact Lens Solution Reduces the Efficacy of the Disinfectant

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.

Why does Contact Lens Solution Evaporate Overnight?

It has been observed that contact lens solution sometimes evaporate overnight in contact lens cases and sometimes it takes a bit longer; but sooner or later the solution has to evaporate. 

A research study was conducted by Abbot Medical Optics in 2009 which revealed that on evaporation of contact lens solution; many people fail to use fresh contact lens solution after each use. Instead; they prefer “topping off” the multi-purpose solution. Topping off contact lens solution is associated with several eye infections & hence is never recommended. It is better to be safe than sorry.

Reasons of Contact Lens Solution Evaporation

The contact lens solution evaporates because of dry climate and lower levels of humidity. Moreover; the air conditioning may also facilitate quick evaporation. This is why you get dry eyes whilst wearing contact lenses in an air-conditioned building. It is always a good idea to lubricate and re-lubricate your eyes when dryness is noticed at wearing contact lenses.

What to do to Prevent Evaporation of Contact Lens Solution

To prevent evaporation of contact lens solution it is advised to keep your contact lens cases

• Enclosed in a zipper bag. This way you ensure to create a barrier between your lens case and direct open atmosphere. When the cases are not properly capped or are lying in an open atmosphere; the lower humidity levels and hot or dry temperature dries off the solution from cases.
• If you cannot arrange a zipper bag; prevent evaporation by keeping your contact lens cases protected in a lens kit. It also helps preventing direct exposure of contact lens cases to the climatic changes. 

There is a huge chance of contact lens ripping when they turn dry. Do not reuse dried-out contact lenses since it contains risks of corneal abrasions and scratches. Use a quality multipurpose disinfectant to rub, cleanse and disinfect your contact lenses. After every use please discard the previously used solution in cases and fill the chambers with fresh solution every night/morning. (Whatever your cleaning/disinfecting routine is)