Contact Lenses Care

Chemical (Cold) Disinfection. There are several disinfection solutions on the market. Disinfection solutions contain chemicals such as thimerosal and chlorhexidine in sufficient concentration to kill the most common microorganisms. Since the lenses remain in the solution for long periods of time, they are kept wet and free of deposits.

The cold disinfection process is simple, and only slightly more inconvenient than storing hard contact lenses. After cleaning and rinsing the contact lenses with saline, they are placed in a special storage/ disinfection case, covered with the disinfection solution and left for at least four hours, usually overnight. Make certain that the storage case is rinsed daily with hot tap water and that it is free of any impurities before use. The lenses are then rinsed again with saline before insertion. Because of its relative convenience and simplicity, many contact lens wearers prefer this method over thermal sterilization, especially those who travel frequently. Unfortunately, the soft-lens plastic absorbs a certain amount of the preservatives contained in the solution, and after a while the wearer may develop an allergy to the chemicals. Approximately one fifth of those who start out with chemical disinfection will eventually change to heat disinfection because of this allergic reaction.

On the horizon are different disinfecting systems that don’t contain the two preservatives named above. One utilizes hydrogen peroxide, a system that has been used by doctors in this country, and outside the U.S. by consumers for years. Another utilizes sorbate, or sorbic acid, and is now available in the U.S.

Thermal (Heat) Disinfection. A safe, effective alternative to cold disinfection is heat, which will also destroy harmful bacteria. After lenses are cleaned and rinsed with saline, they are placed in a special case containing saline solution. The case is placed in the thermal unit, which heats up after you switch it on. In older units there is a well into which you pour distilled water. When this water has boiled away, the lenses are sterile. Newer units utilize dry heat. The unit shuts off automatically, and most people sterilize their lenses before going to bed and let them stay in the unit overnight.

The process actually takes less than an hour, including the time required for the lenses to cool before they can be reinserted. The problem with heat sterilization is that many wearers find it a nuisance. In addition, incomplete cleansing and rinsing of the lenses before sterilization may cause deposits to be baked into the lens surface. This method is also tougher on the plastic and may shorten the life of the lenses. There are certain lenses (such as the extended-wear lenses, Perma-Lens, Hydrocurve, and Sauflon) that hold up particularly badly under high heat sterilization. You should consider investing in a newer “dry,” “low” heat thermal unit if you’ve been using an older model. The newer models are smaller, function with a lower but equally effective temperature, and are easier on the lenses. Also, you needn’t put distilled water into the lower chamber, thus adding to the convenience.

Occasionally a heating unit will malfunction by failing to turn off, turning off soo soon, or not turning on at all. Though a nuisance, this is no cause for panic. As an alternative you can place the lenses in their carrying case in a pan of boiling water for thirty minutes. Remove the case from the pan and let the saline and lenses cool to complete the process. This method may also be used when traveling if you forget or decide not to bring your heating unit with you.

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