lenses, which have a stronger adherence to the eye surface, this technique is less suitable. A soft contact lens may be removed by pinching the edge between the thumb and index finger. Moving the lens off the cornea first can improve comfort during removal and reduce risk of scratching the cornea with a fingernail. It is also possible to push or pull a soft lens far enough to the side or bottom of the eyeball to get it to fold then fall out, without pinching and thereby damaging it. If these techniques are used with a rigid lens, it may scratch the cornea. There are also small tools specifically for removing lenses. Usually made of flexible plastic, they resemble small tweezers, or plungers that suction onto the front of the lens. Typically, these tools are used only with rigid lenses. Extreme care must be exercised when using mechanical tools or fingernails to insert or remove contact lenses. Care Lens care varies depending on material and wear schedule. Daily disposables are discarded after a single use and thus require no cleaning. Other lenses need regular cleaning and disinfecting to prevent surface coating and infections. There are many ways to clean and care for contact lenses, typically called care systems or lens solutions: Multipurpose solutions The main attraction of multipurpose solutions is that the same solution can clean, rinse, disinfect and store lenses. Some multipurpose solutions also contain ingredients that improve the surface wettability and comfort of silicone hydrogel lenses. Studies showed that multipurpose solutions are ineffective against Acanthamoebae. There is preliminary research on creating a new multipurpose solution that kills amoeba. Hydrogen peroxide contact solutions Hydrogen peroxide can be used to disinfect contact lenses. Care should be taken not to get hydrogen peroxide in the eye because it is very painful and irritating. With "two-step" products, the hydrogen peroxide must be rinsed away with saline before the lenses may be worn. "One-step" systems allow the hydrogen peroxide to react completely, becoming pure water. Thus "one-step" hydrogen peroxide systems do not require the lenses to be rinsed before insertion, provided the solution has been given enough time to react. An exposure time of 2-3 hours to 3% (non neutralized solution) is sufficient to kill bacteria, HIV, fungi, and Acanthamoeba. This can be achieved by using a "two-step" product or a "one-step" tablet system if the catalytic tablet isn't added before 2-3 hours.