Most multipurpose contact lens solutions contain three classes of ingredients: surfactants, disinfectants and enzymatic cleaners. The disinfectant is designed to kill bacteria, while the surfactant removes any debris that might be stuck to the lens. The enzymatic cleaner dissolves protein that may have been deposited through contact with the eye.
Multipurpose contact lens solutions generally require users to scrub their lenses briefly and gently to remove debris, then soak them in the solution for enzymatic cleaning and disinfection. The solutions may also contain buffering agents to reduce the harshness of any cleaning chemicals and lubricants to make the lenses slip into the eyes easier.
In addition to multipurpose solutions, there are peroxide-based cleaning solutions. These use a diluted hydrogen peroxide solution to clean, disinfect and remove protein all at once and are very efficient at keeping lenses like new. They require a special case, however, that contains a metal disc to react with the solution and neutralize the peroxide. Using this solution without the neutralizer can cause burning and intense eye pain, so these products should only be used as directed.
Saline solution is the simplest form of contact lens solution, but is only good for rinsing and storing lenses. Saline has no disinfecting capabilities, and use of saline instead of a proper contact lens cleaning and disinfecting solution can lead to an eye infection.