I use a contact solution that is hydrogen peroxide based. That is, the solution is hydrogen peroxide. The solution is put into a special case with a platinum disc at the bottom. The disc acts a catalyst for a chemical reaction. In the end I am left with clean contacts in what is effectively water. If wanted, you can read more about the product here.
Am I allowed to use this solution on Shabbos? Is there a melacha involved? What might a chemical reaction be likened to?