When the combined solution is added directly to the case containing the platinum disc, the hydrogen peroxide decomposes leaving a non-preserved saline. The major disadvantage of this one-step system is that it takes six hours to complete the neutralization process. In the two-step systems, neutralization is completed in 10 to 25 minutes. However, a severe eye irritation may occur if the patient forgets to perform the neutralization procedure. Recently, two chlorine-based systems have been added to the group of soft lens chemical disinfecting systems.
Disinfection is achieved by dissolving the tablet in non-preserved saline.
The chlorine released disinfects the lens in approximately four hours. The main advantages of these chlorine-based systems are simplicity in use, effective bactericidal activity and minimal risk of sensitivity. It is claimed that little or no ocular irritation is experienced from the solution should the patient inadvertently insert the lens immediately after dissolving the tablet. However, the system is not recommended for tinted soft lenses because chlorine bleaches out the tint. Other Disinfecting Systems Ultrasound and microwave irradiation have been tested for soft lens sterilization.