The storage case is an integral part of the contact lens care routine, serving as a sterile environment for disinfection and hydration. Proper use of the case, especially regarding the solution volume, is necessary for maintaining lens integrity and safeguarding eye health. The solution’s disinfecting properties actively work to kill microorganisms, but this process is only effective when the lenses are fully submerged. Understanding the correct amount ensures the entire lens surface is cleaned and prevents severe eye infections.
The Specifics of Filling the Case
The general rule for multipurpose solutions is to fill the case just enough to completely cover the lens when it is placed inside. Many modern contact lens cases feature a clearly marked fill line inside each well, which serves as the most accurate guide for the required volume. This line indicates the minimum amount of solution needed to ensure the lens is fully submerged and surrounded by the disinfecting agent. It is often helpful to place a small amount of fresh solution in the well before inserting the lens, allowing it to float, and then topping off the liquid until the fill line is reached.
Specialized systems, such as those using hydrogen peroxide, require strict adherence to their unique cases and specific fill instructions. These cases contain a neutralizing disc, typically made of platinum, which converts the hydrogen peroxide solution into a gentle saline over several hours. Manufacturers direct users to fill the case precisely to the marked line to ensure the solution is neutralized correctly and the entire lens is disinfected. Failure to follow these instructions can result in a painful chemical burn if unneutralized hydrogen peroxide touches the eye.
Consequences of Underfilling or Overfilling
Using too little solution creates a dangerous environment where the lens is not fully submerged, which significantly compromises disinfection. Any portion of the lens exposed to the air will not be cleaned, allowing bacteria, fungi, and other microbes to survive and multiply on the lens surface. Underfilling can also cause the exposed part of the lens to dry out, leading to warping or a change in shape that makes the lens uncomfortable or unusable upon reinsertion. A partially dried lens can cause corneal abrasion or irritation.
Overfilling the case results in unnecessary waste and introduces a contamination risk. When the cap is screwed onto an overfilled well, the excess solution spills out and runs down the outside threads of the case. Microorganisms from the surrounding environment, such as a bathroom counter, can then adhere to the wet threads. When the cap is opened again, these microbes can be reintroduced into the fresh solution, potentially leading to a contact lens-related infection. While it may seem economical to use less solution, the precise volume is necessary for the chemical disinfection process to work effectively and safely.
Maintaining Case Hygiene
Beyond the correct volume of solution, the overall cleanliness of the case is important for preventing eye infections. After removing lenses, the used solution must be immediately discarded and never reused or “topped off” with fresh solution. Reusing solution significantly reduces its disinfecting power and increases the risk of contamination.
After emptying the old solution, the case should be rinsed thoroughly with a fresh multi-purpose or saline solution, but never with tap water. Tap water can contain Acanthamoeba, a microorganism that can cause a severe, sight-threatening eye infection called Acanthamoeba keratitis. The rinsed case should then be left uncapped and allowed to air-dry upside down on a clean surface to minimize bacterial growth and keep residual moisture from accumulating. Eye care professionals generally advise replacing the contact lens case itself at least every three months, or whenever you open a new bottle of solution, because the plastic can degrade and harbor biofilm over time.