There are three leading brands of peroxide system in the UK: 10/10, Oxysept and Perform. They differ in the neutralising agent used in the second step of the system. In 10/10, the neutraliser contains sodium pyruvate; this is a chemical produced naturally in the body as a byproduct of metabolism and is well tolerated. The neutraliser in Oxysept is an enzyme called catalase; in practice, few problems arise with this, In Perform, the neutraliser is sodium thiosulphate. This is a less powerful agent than sodium pyruvate or catalase. Follow the manufacturer’s instructions carefully and it should prove acceptable.

Some other modern preservative-free systems use as their germ-killing agent chemicals which release free chlorine in the process. These type of systems do not require a neutralising agent; they are cheaper to buy and less time-consuming to use. In theory, the chlorine released should disperse during soaking overnight and not cause problems in the morning. In practice, most people do not have problems with this type of system but even some people who are not chemically sensitive find that they get irritation from the minute traces of chlorine left on the lens.

On balance, the more expensive and less convenient peroxide plus neutralising agent systems, such as 10/10 and Oxysept, are a better choice for the chemically sensitive.

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