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Before you touch your contacts or any part of your case you need to wash your hands with warm water and soap. Hold your hands under the water and sing the "Birthday Song" to ensure that they are properly clean. Being vigilant about handwashing will prevent the transfer of bacteria from your hands to your eyes. For best results, use an all-natural soap that does not contain additional fragrances or moisturizers. These chemicals can transfer from your hands to the case and then to your eyes. When you know you are going to handle your case or contacts, dry your hands off with a lint-free towel. This will prevent fibers from making their way into your case and causing eye irritation. Grab your case and unscrew the lids from the wells (if they are closed). Set the lids aside. Turn the case upside down over your sink and drain out the old solution. Shake the case a bit to remove any leftover moisture. This may sound like common sense, but check that you contacts are not in the case before you empty it. If you see leftover lens solution in your case, resist the urge to add solution to it and move on. Reusing solution in this way lessens its sanitizing effects and can lead to a bacterial infection.
Wash your hands. Empty your case. Never "top-off" the solution.